diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 38a49b60219..0cbb31def30 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -177,8 +177,75 @@ jobs:
           cpp-coveralls -i src -i include -e src/external --exclude-pattern "/usr/*" --dump cpp_cov.json
           coveralls --merge=cpp_cov.json --service=github
 
+  win:
+    runs-on: windows-latest
+    strategy:
+      matrix:
+        python-version: ["3.11"]
+        omp: [n, y]
+
+        include:
+          - python-version: "3.11"
+            omp: n
+          - python-version: "3.11"
+            omp: y
+    name: "Windows Python ${{ matrix.python-version }} (omp=${{ matrix.omp }})"
+
+    env:
+      OMP: ${{ matrix.omp }}
+      EVENT: ${{ matrix.event }}
+      NPY_DISABLE_CPU_FEATURES: "AVX512F AVX512_SKX"
+      OPENBLAS_NUM_THREADS: 1
+      # libfabric complains about fork() as a result of using Python multiprocessing.
+      # We can work around it with RDMAV_FORK_SAFE=1 in libfabric < 1.13 and with
+      # FI_EFA_FORK_SAFE=1 in more recent versions.
+      RDMAV_FORK_SAFE: 1
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Environment Variables
+        shell: pwsh
+        run: |
+          [Environment]::SetEnvironmentVariable("OPENMC_CROSS_SECTIONS", "$Env:GITHUB_WORKSPACE\nndc_hdf5\cross_sections.xml", 'Machine')
+          [Environment]::SetEnvironmentVariable("OPENMC_ENDF_DATA", "$Env:GITHUB_WORKSPACE\endf-b-vii.1", 'Machine')
+
+      - name: Cache XS
+        uses: actions/cache@v4
+        with:
+          path: |
+            ${{github.workspace}}\nndc_hdf5
+            ${{github.workspace}}\endf-b-vii.1
+          key: ${{ runner.os }}-build-xs-cache
+
+      - name: Install
+        shell: pwsh
+        run: |
+          ${{github.workspace}}\tools\ci\gha-install.ps1
+
+      - name: Before
+        shell: pwsh
+        run: ${{github.workspace}}\tools\ci\download-xs.ps1
+
+      - name: Test
+        shell: pwsh
+        run: |
+          ctest --output-on-failure -C Release ${{ github.workspace }}\build\
+          ${{github.workspace}}\tools\ci\gha-script.ps1
+
+      - name: Setup tmate debug session
+        continue-on-error: true
+        if: ${{ contains(env.COMMIT_MESSAGE, '[gha-debug]') }}
+        uses: mxschmitt/action-tmate@v3
+        timeout-minutes: 10
+
   finish:
-    needs: main
+    needs: [win, main]
     runs-on: ubuntu-latest
     steps:
       - name: Coveralls Finished
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4dff35418f0..00e3dea83ae 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -95,6 +95,11 @@ endif()
 
 if(OPENMC_USE_OPENMP)
   find_package(OpenMP REQUIRED)
+
+  if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+    # Special flag to get OpenMP to work on Windows with MSVC
+    list(APPEND cxxflags /openmp:llvm)
+  endif()
 endif()
 
 #===============================================================================
@@ -167,6 +172,12 @@ if(NOT DEFINED HDF5_PREFER_PARALLEL)
   endif()
 endif()
 
+if (MSVC)
+  # To avoid problems with loading DLLs on Windows in the Python API,
+  # we should try to link libhdf5 statically.
+  set(HDF5_USE_STATIC_LIBRARIES TRUE)
+endif()
+
 find_package(HDF5 REQUIRED COMPONENTS C HL)
 
 # Remove HDF5 transitive dependencies that are system libraries
@@ -211,24 +222,22 @@ endif()
 
 # Skip for Visual Studio which has its own configurations through GUI
 if(NOT MSVC)
+  set(CMAKE_POSITION_INDEPENDENT_CODE ON)
 
-set(CMAKE_POSITION_INDEPENDENT_CODE ON)
-
-if(OPENMC_ENABLE_PROFILE)
-  list(APPEND cxxflags -g -fno-omit-frame-pointer)
-endif()
+  if(OPENMC_ENABLE_PROFILE)
+    list(APPEND cxxflags -g -fno-omit-frame-pointer)
+  endif()
 
-if(OPENMC_ENABLE_COVERAGE)
-  list(APPEND cxxflags --coverage)
-  list(APPEND ldflags --coverage)
+  if(OPENMC_ENABLE_COVERAGE)
+    list(APPEND cxxflags --coverage)
+    list(APPEND ldflags --coverage)
+  endif()
 endif()
 
 # Show flags being used
 message(STATUS "OpenMC C++ flags: ${cxxflags}")
 message(STATUS "OpenMC Linker flags: ${ldflags}")
 
-endif()
-
 #===============================================================================
 # Update git submodules as needed
 #===============================================================================
@@ -446,20 +455,31 @@ list(APPEND libopenmc_SOURCES
   src/external/quartic_solver.cpp
   src/external/Faddeeva.cc)
 
-# For Visual Studio compilers
+#===============================================================================
+# openmc library
+#===============================================================================
+add_library(libopenmc SHARED ${libopenmc_SOURCES})
+add_library(OpenMC::libopenmc ALIAS libopenmc)
+
+# For compilers on Windows
 if(MSVC)
-  # Use static library (otherwise explicit symbol portings are needed)
-  add_library(libopenmc STATIC ${libopenmc_SOURCES})
+  # This ensures that all function/class method symbols are exported, without
+  # needing to add the export macros in the source.
+  set_target_properties(libopenmc PROPERTIES WINDOWS_EXPORT_ALL_SYMBOLS ON)
+
+  # This compile definition is needed to make sure that the correct macros
+  # are used for exporting symbols in the dll. While the
+  # WINDOWS_EXPORT_ALL_SYMBOLS exports all function/class symbols, it
+  # unfortunately does not work on global variables, which still need the macro.
+  target_compile_definitions(libopenmc PRIVATE -DOPENMC_DLL_EXPORTS)
 
   # To use the shared HDF5 libraries on Windows, the H5_BUILT_AS_DYNAMIC_LIB
   # compile definition must be specified.
-  target_compile_definitions(libopenmc PRIVATE -DH5_BUILT_AS_DYNAMIC_LIB)
-else()
-  add_library(libopenmc SHARED ${libopenmc_SOURCES})
+  if (NOT HDF5_USE_STATIC_LIBRARIES)
+    target_compile_definitions(libopenmc PRIVATE -DH5_BUILT_AS_DYNAMIC_LIB)
+  endif()
 endif()
 
-add_library(OpenMC::libopenmc ALIAS libopenmc)
-
 # Avoid vs error lnk1149 :output filename matches input filename
 if(NOT MSVC)
   set_target_properties(libopenmc PROPERTIES OUTPUT_NAME openmc)
diff --git a/include/openmc/capi.h b/include/openmc/capi.h
index 54257d09385..b462ea6e7b2 100644
--- a/include/openmc/capi.h
+++ b/include/openmc/capi.h
@@ -284,8 +284,17 @@ extern int OPENMC_E_DATA;
 extern int OPENMC_E_PHYSICS;
 extern int OPENMC_E_WARNING;
 
+// Macro to ensure global variables are exported in Windows DLLs
+#if defined(_WIN32) && defined(OPENMC_DLL_EXPORTS)
+#define OPENMC_API __declspec(dllexport)
+#elif defined(_WIN32)
+#define OPENMC_API __declspec(dllimport)
+#else
+#define OPENMC_API
+#endif
+
 // Global variables
-extern char openmc_err_msg[256];
+extern char OPENMC_API openmc_err_msg[256];
 
 #ifdef __cplusplus
 }
diff --git a/include/openmc/constants.h b/include/openmc/constants.h
index 252194528c7..afc7ac28fb9 100644
--- a/include/openmc/constants.h
+++ b/include/openmc/constants.h
@@ -365,6 +365,19 @@ enum class GeometryType { CSG, DAG };
 // representations. This value represents no surface.
 constexpr int32_t SURFACE_NONE {0};
 
+//==============================================================================
+// Shared Libraries on Windows need the functions/classes/variables to be
+// exposed to be declared with this special keyword "__declspec(dllexport)".
+// We use a macro for this, so that it is only exported on Windows.
+
+#if defined(_WIN32) && defined(OPENMC_DLL_EXPORTS)
+#define OPENMC_API __declspec(dllexport)
+#elif defined(_WIN32)
+#define OPENMC_API __declspec(dllimport)
+#else
+#define OPENMC_API
+#endif
+
 } // namespace openmc
 
 #endif // OPENMC_CONSTANTS_H
diff --git a/include/openmc/dagmc.h b/include/openmc/dagmc.h
index 82ef1b644f3..bd91090eb28 100644
--- a/include/openmc/dagmc.h
+++ b/include/openmc/dagmc.h
@@ -1,9 +1,11 @@
 #ifndef OPENMC_DAGMC_H
 #define OPENMC_DAGMC_H
 
+#include "openmc/constants.h" // Needed for OPENMC_API
+
 namespace openmc {
-extern "C" const bool DAGMC_ENABLED;
-extern "C" const bool UWUW_ENABLED;
+extern "C" const bool OPENMC_API DAGMC_ENABLED;
+extern "C" const bool OPENMC_API UWUW_ENABLED;
 } // namespace openmc
 
 // always include the XML interface header
diff --git a/include/openmc/event.h b/include/openmc/event.h
index 2d215a10e46..6004d0ffbcd 100644
--- a/include/openmc/event.h
+++ b/include/openmc/event.h
@@ -7,6 +7,8 @@
 #include "openmc/particle.h"
 #include "openmc/shared_array.h"
 
+#include <tuple>
+
 namespace openmc {
 
 //==============================================================================
diff --git a/include/openmc/geometry.h b/include/openmc/geometry.h
index 107cc7d1f3e..2e31f7c49e1 100644
--- a/include/openmc/geometry.h
+++ b/include/openmc/geometry.h
@@ -10,7 +10,7 @@
 
 namespace openmc {
 
-class BoundaryInfo;
+struct BoundaryInfo;
 class GeometryState;
 
 //==============================================================================
diff --git a/include/openmc/mcpl_interface.h b/include/openmc/mcpl_interface.h
index e5c182280c8..d67abcb02d8 100644
--- a/include/openmc/mcpl_interface.h
+++ b/include/openmc/mcpl_interface.h
@@ -1,6 +1,7 @@
 #ifndef OPENMC_MCPL_INTERFACE_H
 #define OPENMC_MCPL_INTERFACE_H
 
+#include "openmc/constants.h"
 #include "openmc/particle_data.h"
 #include "openmc/span.h"
 #include "openmc/vector.h"
@@ -13,7 +14,7 @@ namespace openmc {
 // Constants
 //==============================================================================
 
-extern "C" const bool MCPL_ENABLED;
+extern "C" const bool OPENMC_API MCPL_ENABLED;
 
 //==============================================================================
 // Functions
diff --git a/include/openmc/mesh.h b/include/openmc/mesh.h
index 5a727c2b6f1..65e32b33eeb 100644
--- a/include/openmc/mesh.h
+++ b/include/openmc/mesh.h
@@ -11,6 +11,7 @@
 #include "xtensor/xtensor.hpp"
 
 #include "openmc/bounding_box.h"
+#include "openmc/constants.h" // for OPENMC_API
 #include "openmc/error.h"
 #include "openmc/memory.h" // for unique_ptr
 #include "openmc/particle.h"
@@ -50,7 +51,7 @@ enum class ElementType { UNSUPPORTED = -1, LINEAR_TET, LINEAR_HEX };
 // Global variables
 //==============================================================================
 
-extern "C" const bool LIBMESH_ENABLED;
+extern "C" const bool OPENMC_API LIBMESH_ENABLED;
 
 class Mesh;
 
@@ -578,7 +579,7 @@ class CylindricalMesh : public PeriodicStructuredMesh {
 
   inline int sanitize_angular_index(int idx, bool full, int N) const
   {
-    if ((idx > 0) and (idx <= N)) {
+    if ((idx > 0) && (idx <= N)) {
       return idx;
     } else if (full) {
       return (idx + N - 1) % N + 1;
@@ -640,7 +641,7 @@ class SphericalMesh : public PeriodicStructuredMesh {
 
   inline int sanitize_angular_index(int idx, bool full, int N) const
   {
-    if ((idx > 0) and (idx <= N)) {
+    if ((idx > 0) && (idx <= N)) {
       return idx;
     } else if (full) {
       return (idx + N - 1) % N + 1;
diff --git a/include/openmc/message_passing.h b/include/openmc/message_passing.h
index a1641a9069e..23b79b4f676 100644
--- a/include/openmc/message_passing.h
+++ b/include/openmc/message_passing.h
@@ -7,6 +7,7 @@
 #include <mpi.h>
 #endif
 
+#include "openmc/constants.h"
 #include "openmc/vector.h"
 
 namespace openmc {
@@ -14,7 +15,7 @@ namespace mpi {
 
 extern int rank;
 extern int n_procs;
-extern bool master;
+extern bool OPENMC_API master;
 
 #ifdef OPENMC_MPI
 extern MPI_Datatype source_site;
diff --git a/include/openmc/settings.h b/include/openmc/settings.h
index 9017b2d080b..039f3e264a3 100644
--- a/include/openmc/settings.h
+++ b/include/openmc/settings.h
@@ -136,9 +136,10 @@ extern ResScatMethod res_scat_method; //!< resonance upscattering method
 extern double res_scat_energy_min; //!< Min energy in [eV] for res. upscattering
 extern double res_scat_energy_max; //!< Max energy in [eV] for res. upscattering
 extern vector<std::string>
-  res_scat_nuclides;           //!< Nuclides using res. upscattering treatment
-extern RunMode run_mode;       //!< Run mode (eigenvalue, fixed src, etc.)
-extern SolverType solver_type; //!< Solver Type (Monte Carlo or Random Ray)
+  res_scat_nuclides; //!< Nuclides using res. upscattering treatment
+extern RunMode OPENMC_API run_mode; //!< Run mode (eigenvalue, fixed src, etc.)
+extern SolverType OPENMC_API
+  solver_type; //!< Solver Type (Monte Carlo or Random Ray)
 extern std::unordered_set<int>
   sourcepoint_batch; //!< Batches when source should be written
 extern std::unordered_set<int>
diff --git a/include/openmc/shared_array.h b/include/openmc/shared_array.h
index 7e9ef28c580..fc9a975c781 100644
--- a/include/openmc/shared_array.h
+++ b/include/openmc/shared_array.h
@@ -72,13 +72,23 @@ class SharedArray {
   {
     // Atomically capture the index we want to write to
     int64_t idx;
+#if _WIN32 && !__INTEL_COMPILER
+#pragma omp atomic capture
+    idx = size_++;
+#else
 #pragma omp atomic capture seq_cst
     idx = size_++;
+#endif
 
     // Check that we haven't written off the end of the array
     if (idx >= capacity_) {
+#if _WIN32 && !__INTEL_COMPILER
+#pragma omp atomic write
+      size_ = capacity_;
+#else
 #pragma omp atomic write seq_cst
       size_ = capacity_;
+#endif
       return -1;
     }
 
diff --git a/include/openmc/tallies/filter.h b/include/openmc/tallies/filter.h
index ee635b18327..019e6f8a375 100644
--- a/include/openmc/tallies/filter.h
+++ b/include/openmc/tallies/filter.h
@@ -150,7 +150,7 @@ class Filter {
 
 namespace model {
 extern "C" int32_t n_filters;
-extern std::unordered_map<int, int> filter_map;
+extern std::unordered_map<int, int> OPENMC_API filter_map;
 extern vector<unique_ptr<Filter>> tally_filters;
 } // namespace model
 
diff --git a/openmc/deplete/pool.py b/openmc/deplete/pool.py
index 27ecaa4dd8b..705980ec67b 100644
--- a/openmc/deplete/pool.py
+++ b/openmc/deplete/pool.py
@@ -10,10 +10,17 @@
 
 from openmc.mpi import comm
 
+import sys
+
 # Configurable switch that enables / disables the use of
 # multiprocessing routines during depletion
 USE_MULTIPROCESSING = True
 
+# Not sure why, but using multiprocessing on Windows leads to many transport
+# simulations being run over eachother and leads to catastrophe.
+if sys.platform == 'win32':
+    USE_MULTIPROCESSING = False
+
 # Allow user to override the number of worker processes to use for depletion
 # calculations
 NUM_PROCESSES = None
diff --git a/openmc/lib/__init__.py b/openmc/lib/__init__.py
index 15642b42be3..20cf8691c50 100644
--- a/openmc/lib/__init__.py
+++ b/openmc/lib/__init__.py
@@ -19,12 +19,20 @@
 
 
 # Determine shared-library suffix
-if sys.platform == 'darwin':
+if sys.platform == 'win32':
+    _suffix = 'dll'
+elif sys.platform == 'darwin':
     _suffix = 'dylib'
 else:
     _suffix = 'so'
 
 if os.environ.get('READTHEDOCS', None) != 'True':
+    # To load the DLL on Windows without error, we need to add the path of
+    # the DLL. We get the directory from the path of this file.
+    if sys.platform == 'win32':
+        dll_path = os.path.dirname(os.path.abspath(__file__))
+        os.add_dll_directory(dll_path)
+
     # Open shared library
     _filename = importlib.resources.files(__name__) / f'libopenmc.{_suffix}'
     _dll = CDLL(str(_filename))  # TODO: Remove str() when Python 3.12+
diff --git a/openmc/model/model.py b/openmc/model/model.py
index c19c8ac9f15..7446a62dfbe 100644
--- a/openmc/model/model.py
+++ b/openmc/model/model.py
@@ -1027,7 +1027,7 @@ def plot(
 
             if outline:
                 # Combine R, G, B values into a single int
-                rgb = (img * 256).astype(int)
+                rgb = img.astype(int) * 256
                 image_value = (rgb[..., 0] << 16) + \
                     (rgb[..., 1] << 8) + (rgb[..., 2])
 
diff --git a/pyproject.toml b/pyproject.toml
index 6e8ed798e78..9ecceed457a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -65,6 +65,6 @@ exclude = ['tests*']
 [tool.setuptools.package-data]
 "openmc.data.effective_dose" = ["**/*.txt"]
 "openmc.data" = ["*.txt", "*.DAT", "*.json", "*.h5"]
-"openmc.lib" = ["libopenmc.dylib", "libopenmc.so"]
+"openmc.lib" = ["libopenmc.dylib", "libopenmc.so", "libopenmc.dll"]
 
 [tool.setuptools_scm]
diff --git a/src/cell.cpp b/src/cell.cpp
index 4b26992299e..3640a4a501c 100644
--- a/src/cell.cpp
+++ b/src/cell.cpp
@@ -482,7 +482,9 @@ Region::Region(std::string region_spec, int32_t cell_id)
     auto it = std::find(expression_.begin(), expression_.end(), OP_COMPLEMENT);
     while (it != expression_.end()) {
       // Erase complement
-      expression_.erase(it);
+      it = expression_.erase(it);
+      if (it == expression_.end())
+        break; // Shouldn't happen, but to be safe
 
       // Define stop given left parenthesis or not
       auto stop = it;
@@ -536,7 +538,7 @@ Region::Region(std::string region_spec, int32_t cell_id)
     if (simple_) {
       for (auto it = expression_.begin(); it != expression_.end(); it++) {
         if (*it == OP_INTERSECTION || *it > OP_COMPLEMENT) {
-          expression_.erase(it);
+          it = expression_.erase(it);
           it--;
         }
       }
diff --git a/src/cross_sections.cpp b/src/cross_sections.cpp
index b1bfde03d13..a7350f45029 100644
--- a/src/cross_sections.cpp
+++ b/src/cross_sections.cpp
@@ -71,16 +71,14 @@ Library::Library(pugi::xml_node node, const std::string& directory)
   if (!check_for_node(node, "path")) {
     fatal_error("Missing library path");
   }
-  std::string path = get_node_value(node, "path");
-
-  if (starts_with(path, "/")) {
-    path_ = path;
-  } else if (ends_with(directory, "/")) {
-    path_ = directory + path;
-  } else if (!directory.empty()) {
-    path_ = directory + "/" + path;
+  std::filesystem::path path(get_node_value(node, "path"));
+  std::filesystem::path dir(directory);
+  if (path.is_absolute()) {
+    path_ = path.string();
+  } else if (std::filesystem::is_directory(dir)) {
+    path_ = (dir / path).string();
   } else {
-    path_ = path;
+    path_ = path.string();
   }
 
   if (!file_exists(path_)) {
@@ -144,11 +142,11 @@ void read_cross_sections_xml(pugi::xml_node root)
   } else {
     settings::path_cross_sections = get_node_value(root, "cross_sections");
 
-    // If no '/' found, the file is probably in the input directory
-    auto pos = settings::path_cross_sections.rfind("/");
-    if (pos == std::string::npos && !settings::path_input.empty()) {
-      settings::path_cross_sections =
-        settings::path_input + "/" + settings::path_cross_sections;
+    // If the path is relative, it is probably in the input directory
+    std::filesystem::path p(settings::path_cross_sections);
+    if (p.is_relative() && !settings::path_input.empty()) {
+      std::filesystem::path dir(settings::path_input);
+      settings::path_cross_sections = (dir / p).string();
     }
   }
 
diff --git a/src/dagmc.cpp b/src/dagmc.cpp
index 13436088652..6d6274a0765 100644
--- a/src/dagmc.cpp
+++ b/src/dagmc.cpp
@@ -27,9 +27,9 @@
 namespace openmc {
 
 #ifdef DAGMC
-const bool DAGMC_ENABLED = true;
+const bool OPENMC_API DAGMC_ENABLED = true;
 #else
-const bool DAGMC_ENABLED = false;
+const bool OPENMC_API DAGMC_ENABLED = false;
 #endif
 
 #ifdef OPENMC_UWUW
diff --git a/src/error.cpp b/src/error.cpp
index 566950a973c..467bc67c184 100644
--- a/src/error.cpp
+++ b/src/error.cpp
@@ -30,7 +30,7 @@ int OPENMC_E_PHYSICS {-10};
 int OPENMC_E_WARNING {1};
 
 // Error message
-char openmc_err_msg[256];
+char OPENMC_API openmc_err_msg[256];
 
 //==============================================================================
 // Functions
diff --git a/src/external/quartic_solver.cpp b/src/external/quartic_solver.cpp
index 915020ffaa3..34772463130 100644
--- a/src/external/quartic_solver.cpp
+++ b/src/external/quartic_solver.cpp
@@ -7,6 +7,9 @@
 
 namespace oqs {
 
+// TODO: replace with <numbers> when we go for C++20
+constexpr double PI {3.141592653589793238462643383279502884L};
+
 // pow(DBL_MAX,1.0/3.0)/1.618034;
 constexpr double CUBIC_RESCAL_FACT = 3.488062113727083e+102;
 // pow(DBL_MAX,1.0/4.0)/1.618034;
@@ -36,10 +39,10 @@ double solve_cubic_analytic_depressed_handle_inf(double b, double c)
   if (KK < 0.0) {
     double sqrtQ = std::sqrt(Q);
     double theta = std::acos((R / std::abs(Q)) / sqrtQ);
-    if (2.0 * theta < M_PI)
+    if (2.0 * theta < PI)
       return -2.0 * sqrtQ * std::cos(theta / 3.0);
     else
-      return -2.0 * sqrtQ * std::cos((theta + 2.0 * M_PI) / 3.0);
+      return -2.0 * sqrtQ * std::cos((theta + 2.0 * PI) / 3.0);
   } else {
     double A;
     if (std::abs(Q) < std::abs(R))
@@ -68,10 +71,10 @@ double solve_cubic_analytic_depressed(double b, double c)
   if (R2 < Q3) {
     double theta = std::acos(R / std::sqrt(Q3));
     double sqrtQ = -2.0 * std::sqrt(Q);
-    if (2.0 * theta < M_PI)
+    if (2.0 * theta < PI)
       return sqrtQ * std::cos(theta / 3.0);
     else
-      return sqrtQ * std::cos((theta + 2.0 * M_PI) / 3.0);
+      return sqrtQ * std::cos((theta + 2.0 * PI) / 3.0);
   } else {
     double A = -std::copysign(1.0, R) *
                std::pow(std::abs(R) + std::sqrt(R2 - Q3), 1.0 / 3.0);
diff --git a/src/mcpl_interface.cpp b/src/mcpl_interface.cpp
index 83ef6332097..d4b5608d0ad 100644
--- a/src/mcpl_interface.cpp
+++ b/src/mcpl_interface.cpp
@@ -22,9 +22,9 @@ namespace openmc {
 //==============================================================================
 
 #ifdef OPENMC_MCPL
-const bool MCPL_ENABLED = true;
+const bool OPENMC_API MCPL_ENABLED = true;
 #else
-const bool MCPL_ENABLED = false;
+const bool OPENMC_API MCPL_ENABLED = false;
 #endif
 
 //==============================================================================
diff --git a/src/mesh.cpp b/src/mesh.cpp
index 8280177ac13..1c4b7f04b92 100644
--- a/src/mesh.cpp
+++ b/src/mesh.cpp
@@ -64,9 +64,9 @@ namespace openmc {
 //==============================================================================
 
 #ifdef LIBMESH
-const bool LIBMESH_ENABLED = true;
+const bool OPENMC_API LIBMESH_ENABLED = true;
 #else
-const bool LIBMESH_ENABLED = false;
+const bool OPENMC_API LIBMESH_ENABLED = false;
 #endif
 
 // Value used to indicate an empty slot in the hash table. We use -2 because
@@ -1492,7 +1492,7 @@ StructuredMesh::MeshIndex CylindricalMesh::get_indices(
   } else {
     mapped_r[1] = std::atan2(r.y, r.x);
     if (mapped_r[1] < 0)
-      mapped_r[1] += 2 * M_PI;
+      mapped_r[1] += 2 * PI;
   }
 
   MeshIndex idx = StructuredMesh::get_indices(mapped_r, in_mesh);
@@ -1771,7 +1771,7 @@ StructuredMesh::MeshIndex SphericalMesh::get_indices(
     mapped_r[1] = std::acos(r.z / mapped_r.x);
     mapped_r[2] = std::atan2(r.y, r.x);
     if (mapped_r[2] < 0)
-      mapped_r[2] += 2 * M_PI;
+      mapped_r[2] += 2 * PI;
   }
 
   MeshIndex idx = StructuredMesh::get_indices(mapped_r, in_mesh);
diff --git a/src/message_passing.cpp b/src/message_passing.cpp
index 374c1aa7257..fa246a5d7d2 100644
--- a/src/message_passing.cpp
+++ b/src/message_passing.cpp
@@ -5,7 +5,7 @@ namespace mpi {
 
 int rank {0};
 int n_procs {1};
-bool master {true};
+bool OPENMC_API master {true};
 
 #ifdef OPENMC_MPI
 MPI_Comm intracomm {MPI_COMM_NULL};
diff --git a/src/plot.cpp b/src/plot.cpp
index dbc25b21e4d..514a0e4b5e7 100644
--- a/src/plot.cpp
+++ b/src/plot.cpp
@@ -1,7 +1,6 @@
 #include "openmc/plot.h"
 
 #include <algorithm>
-#define _USE_MATH_DEFINES // to make M_PI declared in Intel and MSVC compilers
 #include <cmath>
 #include <cstdio>
 #include <fstream>
@@ -1180,7 +1179,7 @@ std::pair<Position, Direction> RayTracePlot::get_pixel_ray(
   int horiz, int vert) const
 {
   // Compute field of view in radians
-  constexpr double DEGREE_TO_RADIAN = M_PI / 180.0;
+  constexpr double DEGREE_TO_RADIAN = PI / 180.0;
   double horiz_fov_radians = horizontal_field_of_view_ * DEGREE_TO_RADIAN;
   double p0 = static_cast<double>(pixels_[0]);
   double p1 = static_cast<double>(pixels_[1]);
@@ -1535,9 +1534,12 @@ void SolidRayTracePlot::create_output() const
   size_t height = pixels_[1];
   ImageData data({width, height}, not_found_);
 
+  const auto pixels_0 = pixels_[0];
+  const auto pixels_1 = pixels_[1];
+
 #pragma omp parallel for schedule(dynamic) collapse(2)
-  for (int horiz = 0; horiz < pixels_[0]; ++horiz) {
-    for (int vert = 0; vert < pixels_[1]; ++vert) {
+  for (int horiz = 0; horiz < pixels_0; ++horiz) {
+    for (int vert = 0; vert < pixels_1; ++vert) {
       // RayTracePlot implements camera ray generation
       std::pair<Position, Direction> ru = get_pixel_ray(horiz, vert);
       PhongRay ray(ru.first, ru.second, *this);
diff --git a/src/random_ray/flat_source_domain.cpp b/src/random_ray/flat_source_domain.cpp
index cd073f35077..d45dd24a3ce 100644
--- a/src/random_ray/flat_source_domain.cpp
+++ b/src/random_ray/flat_source_domain.cpp
@@ -1012,13 +1012,15 @@ void FlatSourceDomain::apply_external_source_to_cell_and_children(
 
 void FlatSourceDomain::count_external_source_regions()
 {
-  n_external_source_regions_ = 0;
-#pragma omp parallel for reduction(+ : n_external_source_regions_)
+  // Must use temporary accumulator variable for OpenMP on Windows
+  int64_t tmp_n_external_source_regions {0};
+#pragma omp parallel for reduction(+ : tmp_n_external_source_regions)
   for (int64_t sr = 0; sr < n_source_regions(); sr++) {
     if (source_regions_.external_source_present(sr)) {
-      n_external_source_regions_++;
+      tmp_n_external_source_regions++;
     }
   }
+  n_external_source_regions_ = tmp_n_external_source_regions;
 }
 
 void FlatSourceDomain::convert_external_sources()
diff --git a/src/random_ray/random_ray_simulation.cpp b/src/random_ray/random_ray_simulation.cpp
index 40a08c3af7a..58787909f67 100644
--- a/src/random_ray/random_ray_simulation.cpp
+++ b/src/random_ray/random_ray_simulation.cpp
@@ -465,14 +465,17 @@ void RandomRaySimulation::simulate()
       // Start timer for transport
       simulation::time_transport.start();
 
-// Transport sweep over all random rays for the iteration
+      // Transport sweep over all random rays for the iteration
+      // Must use temporary accumulator variable for OpenMP on Windows
+      uint64_t tmp_total_geometric_intersections {0};
 #pragma omp parallel for schedule(dynamic)                                     \
-  reduction(+ : total_geometric_intersections_)
+  reduction(+ : tmp_total_geometric_intersections)
       for (int i = 0; i < settings::n_particles; i++) {
         RandomRay ray(i, domain_.get());
-        total_geometric_intersections_ +=
+        tmp_total_geometric_intersections +=
           ray.transport_history_based_single_ray();
       }
+      total_geometric_intersections_ = tmp_total_geometric_intersections;
 
       simulation::time_transport.stop();
 
diff --git a/src/secondary_correlated.cpp b/src/secondary_correlated.cpp
index 0e4891dd3e7..0674c89fa74 100644
--- a/src/secondary_correlated.cpp
+++ b/src/secondary_correlated.cpp
@@ -208,7 +208,7 @@ void CorrelatedAngleEnergy::sample(
   }
 
   // Continuous portion
-  double c_k1;
+  double c_k1 = 0.;
   for (int j = n_discrete; j < end; ++j) {
     k = j;
     c_k1 = distribution_[l].c[k + 1];
diff --git a/src/settings.cpp b/src/settings.cpp
index c8230a10f1d..1282c6ab939 100644
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -120,8 +120,8 @@ ResScatMethod res_scat_method {ResScatMethod::rvs};
 double res_scat_energy_min {0.01};
 double res_scat_energy_max {1000.0};
 vector<std::string> res_scat_nuclides;
-RunMode run_mode {RunMode::UNSET};
-SolverType solver_type {SolverType::MONTE_CARLO};
+RunMode OPENMC_API run_mode {RunMode::UNSET};
+SolverType OPENMC_API solver_type {SolverType::MONTE_CARLO};
 std::unordered_set<int> sourcepoint_batch;
 std::unordered_set<int> statepoint_batch;
 std::unordered_set<int> source_write_surf_id;
diff --git a/src/source.cpp b/src/source.cpp
index 8e6eb4f11fd..bb95dddc822 100644
--- a/src/source.cpp
+++ b/src/source.cpp
@@ -381,7 +381,7 @@ SourceSite IndependentSource::sample(uint64_t* seed) const
       site.E = energy_->sample(seed);
 
       // Resample if energy falls above maximum particle energy
-      if (site.E < data::energy_max[p] and
+      if (site.E < data::energy_max[p] &&
           (satisfies_energy_constraints(site.E)))
         break;
 
diff --git a/src/tallies/filter.cpp b/src/tallies/filter.cpp
index 17e57a987c7..83c0dd21467 100644
--- a/src/tallies/filter.cpp
+++ b/src/tallies/filter.cpp
@@ -50,7 +50,7 @@ namespace openmc {
 //==============================================================================
 
 namespace model {
-std::unordered_map<int, int> filter_map;
+std::unordered_map<int, int> OPENMC_API filter_map;
 vector<unique_ptr<Filter>> tally_filters;
 } // namespace model
 
diff --git a/tests/cpp_unit_tests/test_file_utils.cpp b/tests/cpp_unit_tests/test_file_utils.cpp
index 8b0d99d76da..cce8672907f 100644
--- a/tests/cpp_unit_tests/test_file_utils.cpp
+++ b/tests/cpp_unit_tests/test_file_utils.cpp
@@ -5,6 +5,18 @@ using namespace openmc;
 
 TEST_CASE("Test get_file_extension")
 {
+#if defined(_WIN32) || defined(_WIN64)
+  REQUIRE(get_file_extension("rememberthealamo.png") == "png");
+  REQUIRE(get_file_extension("statepoint.20.h5") == "h5");
+  REQUIRE(get_file_extension("wEiRDNaa_ame.h4") == "h4");
+  REQUIRE(get_file_extension("has_directory\\asdf.20.h5") == "h5");
+  REQUIRE(get_file_extension("wasssssup_lol") == "");
+  REQUIRE(get_file_extension("has_directory\\secret_file") == "");
+  REQUIRE(get_file_extension("lovely.dir\\extensionless_file") == "");
+  REQUIRE(get_file_extension("lovely.dir\\statepoint.20.h5") == "h5");
+  REQUIRE(get_file_extension("lovely.dir\\asdf123.cpp") == "cpp");
+
+#else
   REQUIRE(get_file_extension("rememberthealamo.png") == "png");
   REQUIRE(get_file_extension("statepoint.20.h5") == "h5");
   REQUIRE(get_file_extension("wEiRDNaa_ame.h4") == "h4");
@@ -14,21 +26,35 @@ TEST_CASE("Test get_file_extension")
   REQUIRE(get_file_extension("lovely.dir/extensionless_file") == "");
   REQUIRE(get_file_extension("lovely.dir/statepoint.20.h5") == "h5");
   REQUIRE(get_file_extension("lovely.dir/asdf123.cpp") == "cpp");
+#endif
 }
 
 TEST_CASE("Test dir_exists")
 {
+#if defined(_WIN32) || defined(_WIN64)
+  // If this doesn't exist on a Windows system, I have no clue what is happening
+  REQUIRE(dir_exists("C:\\"));
+
+  // if this exists on your system... you deserve for this test to fail
+  REQUIRE(!dir_exists("C:\\asdfa\\asdfasdf\\asdgasodgosuihasjkgh"));
+#else
   // not sure how to test this when running on windows?
   REQUIRE(dir_exists("/"));
 
   // if this exists on your system... you deserve for this test to fail
   REQUIRE(!dir_exists("/asdfa/asdfasdf/asdgasodgosuihasjkgh/"));
+#endif
 }
 
 TEST_CASE("Test file_exists")
 {
+#if defined(_WIN32) || defined(_WIN64)
+  // Note: not clear how to portably test where a file should exist.
+  REQUIRE(!file_exists("C:\\should_not_exist\\really_do_not_make_this_please"));
+#else
   // Note: not clear how to portably test where a file should exist.
   REQUIRE(!file_exists("./should_not_exist/really_do_not_make_this_please"));
+#endif
 }
 
 TEST_CASE("Test dir_name")
diff --git a/tests/regression_tests/cpp_driver/test.py b/tests/regression_tests/cpp_driver/test.py
index b80e82ee0e1..286f0a7377f 100644
--- a/tests/regression_tests/cpp_driver/test.py
+++ b/tests/regression_tests/cpp_driver/test.py
@@ -1,5 +1,6 @@
 from pathlib import Path
 import os
+import sys
 import shutil
 import subprocess
 import textwrap
@@ -11,6 +12,9 @@
 from tests.regression_tests import config
 from tests.testing_harness import PyAPITestHarness
 
+pytestmark = pytest.mark.skipif(
+    sys.platform == 'win32',
+    reason="Cannot use compiled tests on Windows.")
 
 @pytest.fixture
 def cpp_driver(request):
diff --git a/tests/regression_tests/deplete_decay_only/test.py b/tests/regression_tests/deplete_decay_only/test.py
index 4345b86b898..7b9f9af9714 100644
--- a/tests/regression_tests/deplete_decay_only/test.py
+++ b/tests/regression_tests/deplete_decay_only/test.py
@@ -50,7 +50,7 @@ def model():
 @pytest.fixture(scope="module")
 def micro_xs():
     micro_xs_file = Path(__file__).parents[2] / 'micro_xs_simple.csv'
-    return MicroXS.from_csv(micro_xs_file)
+    return MicroXS.from_csv(micro_xs_file, lineterminator='\n')
 
 
 @pytest.fixture(scope="module")
diff --git a/tests/regression_tests/deplete_no_transport/test.py b/tests/regression_tests/deplete_no_transport/test.py
index 63ae584e116..b76c4fa01d8 100644
--- a/tests/regression_tests/deplete_no_transport/test.py
+++ b/tests/regression_tests/deplete_no_transport/test.py
@@ -28,7 +28,7 @@ def fuel():
 @pytest.fixture(scope="module")
 def micro_xs():
     micro_xs_file = Path(__file__).parents[2] / 'micro_xs_simple.csv'
-    return MicroXS.from_csv(micro_xs_file)
+    return MicroXS.from_csv(micro_xs_file, lineterminator='\n')
 
 
 @pytest.fixture(scope="module")
diff --git a/tests/regression_tests/diff_tally/test.py b/tests/regression_tests/diff_tally/test.py
index 89460df9152..5ab1f52f621 100644
--- a/tests/regression_tests/diff_tally/test.py
+++ b/tests/regression_tests/diff_tally/test.py
@@ -109,7 +109,7 @@ def _get_results(self):
         # Extract the relevant data as a CSV string.
         cols = ('d_material', 'd_nuclide', 'd_variable', 'score', 'mean',
                 'std. dev.')
-        return df.to_csv(None, columns=cols, index=False, float_format='%.7e')
+        return df.to_csv(None, columns=cols, index=False, float_format='%.7e', lineterminator='\n')
 
 
 def test_diff_tally():
diff --git a/tests/regression_tests/microxs/test.py b/tests/regression_tests/microxs/test.py
index a35150a1b80..bf36c37099f 100644
--- a/tests/regression_tests/microxs/test.py
+++ b/tests/regression_tests/microxs/test.py
@@ -60,8 +60,8 @@ def test_from_model(model, domain_type):
                 'Xe136', 'Cs135', 'Gd157', 'Gd156']
     _, test_xs = get_microxs_and_flux(model, domains, nuclides, chain_file=CHAIN_FILE)
     if config['update']:
-        test_xs[0].to_csv(f'test_reference_{domain_type}.csv')
+        test_xs[0].to_csv(f'test_reference_{domain_type}.csv', lineterminator='\n')
 
-    ref_xs = MicroXS.from_csv(f'test_reference_{domain_type}.csv')
+    ref_xs = MicroXS.from_csv(f'test_reference_{domain_type}.csv', lineterminator='\n')
 
     np.testing.assert_allclose(test_xs[0].data, ref_xs.data, rtol=1e-11)
diff --git a/tests/regression_tests/source_dlopen/test.py b/tests/regression_tests/source_dlopen/test.py
index 0581d6deec4..c3308a0b8fc 100644
--- a/tests/regression_tests/source_dlopen/test.py
+++ b/tests/regression_tests/source_dlopen/test.py
@@ -1,5 +1,6 @@
 from pathlib import Path
 import os
+import sys
 import shutil
 import subprocess
 import textwrap
@@ -9,6 +10,9 @@
 
 from tests.testing_harness import PyAPITestHarness
 
+pytestmark = pytest.mark.skipif(
+    sys.platform == 'win32',
+    reason="Cannot use compiled tests on Windows.")
 
 @pytest.fixture
 def compile_source(request):
diff --git a/tests/regression_tests/source_parameterized_dlopen/test.py b/tests/regression_tests/source_parameterized_dlopen/test.py
index 151fb37356e..441a125e85f 100644
--- a/tests/regression_tests/source_parameterized_dlopen/test.py
+++ b/tests/regression_tests/source_parameterized_dlopen/test.py
@@ -1,5 +1,6 @@
 from pathlib import Path
 import os
+import sys
 import shutil
 import subprocess
 import textwrap
@@ -9,6 +10,9 @@
 
 from tests.testing_harness import PyAPITestHarness
 
+pytestmark = pytest.mark.skipif(
+    sys.platform == 'win32',
+    reason="Cannot use compiled tests on Windows.")
 
 @pytest.fixture
 def compile_source(request):
diff --git a/tests/regression_tests/surface_tally/test.py b/tests/regression_tests/surface_tally/test.py
index e496ac0f65c..0f2507db480 100644
--- a/tests/regression_tests/surface_tally/test.py
+++ b/tests/regression_tests/surface_tally/test.py
@@ -168,7 +168,7 @@ def _get_results(self):
 
         # Extract the relevant data as a CSV string.
         cols = ('mean', 'std. dev.')
-        return df.to_csv(None, columns=cols, index=False, float_format='%.7e')
+        return df.to_csv(None, columns=cols, index=False, float_format='%.7e', lineterminator='\n')
         return outstr
 
 
diff --git a/tests/unit_tests/test_config.py b/tests/unit_tests/test_config.py
index 4e87de4b7e9..d0e569d2cf5 100644
--- a/tests/unit_tests/test_config.py
+++ b/tests/unit_tests/test_config.py
@@ -4,6 +4,7 @@
 
 import openmc
 import pytest
+from pathlib import Path
 
 
 @pytest.fixture(autouse=True, scope='module')
@@ -45,8 +46,8 @@ def test_config_basics():
 def test_config_patch():
     openmc.config['cross_sections'] = '/path/to/cross_sections.xml'
     with openmc.config.patch('cross_sections', '/path/to/other.xml'):
-        assert str(openmc.config['cross_sections']) == '/path/to/other.xml'
-    assert str(openmc.config['cross_sections']) == '/path/to/cross_sections.xml'
+        assert str(openmc.config['cross_sections']) == str(Path('/path/to/other.xml'))
+    assert str(openmc.config['cross_sections']) == str(Path('/path/to/cross_sections.xml'))
 
 
 def test_config_set_envvar():
diff --git a/tests/unit_tests/test_deplete_independent_operator.py b/tests/unit_tests/test_deplete_independent_operator.py
index c765d065009..88d3f8e8546 100644
--- a/tests/unit_tests/test_deplete_independent_operator.py
+++ b/tests/unit_tests/test_deplete_independent_operator.py
@@ -24,7 +24,7 @@ def test_operator_init():
                 'O16': 4.639065406771322e+22,
                 'O17': 1.7588724018066158e+19}
     flux = 1.0
-    micro_xs = MicroXS.from_csv(ONE_GROUP_XS)
+    micro_xs = MicroXS.from_csv(ONE_GROUP_XS, lineterminator='\n')
     IndependentOperator.from_nuclides(
         volume, nuclides, flux, micro_xs, CHAIN_PATH, nuc_units='atom/cm3')
 
@@ -41,7 +41,7 @@ def test_operator_init():
 
 
 def test_error_handling():
-    micro_xs = MicroXS.from_csv(ONE_GROUP_XS)
+    micro_xs = MicroXS.from_csv(ONE_GROUP_XS, lineterminator='\n')
     fuel = Material(name="oxygen")
     fuel.add_element("O", 2)
     fuel.set_density("g/cc", 1)
diff --git a/tests/unit_tests/test_deplete_microxs.py b/tests/unit_tests/test_deplete_microxs.py
index 073b3f162d1..aebc7c6ff8e 100644
--- a/tests/unit_tests/test_deplete_microxs.py
+++ b/tests/unit_tests/test_deplete_microxs.py
@@ -51,9 +51,9 @@ def test_from_array():
 
 
 def test_csv():
-    ref_xs = MicroXS.from_csv(ONE_GROUP_XS)
-    ref_xs.to_csv('temp_xs.csv')
-    temp_xs = MicroXS.from_csv('temp_xs.csv')
+    ref_xs = MicroXS.from_csv(ONE_GROUP_XS, lineterminator='\n')
+    ref_xs.to_csv('temp_xs.csv', lineterminator='\n')
+    temp_xs = MicroXS.from_csv('temp_xs.csv', lineterminator='\n')
     assert np.all(ref_xs.data == temp_xs.data)
     remove('temp_xs.csv')
 
diff --git a/tools/ci/download-xs.ps1 b/tools/ci/download-xs.ps1
new file mode 100644
index 00000000000..c94cc0f2dd4
--- /dev/null
+++ b/tools/ci/download-xs.ps1
@@ -0,0 +1,14 @@
+$ProgressPreference = 'SilentlyContinue'
+
+# Download HDF5 data
+if (-not (Test-Path "$Env:GITHUB_WORKSPACE\nndc_hdf5")) {
+  Invoke-WebRequest https://anl.box.com/shared/static/teaup95cqv8s9nn56hfn7ku8mmelr95p.xz -OutFile hdf5.xz -UseBasicParsing 
+  tar -xvzf hdf5.xz
+}
+
+# Download ENDF/B-VII.1 distribution
+$Env:ENDF = "$Env:GITHUB_WORKSPACE\endf-b-vii.1"
+if (-not (Test-Path $Env:ENDF)) {
+  Invoke-WebRequest https://anl.box.com/shared/static/4kd2gxnf4gtk4w1c8eua5fsua22kvgjb.xz -OutFile endf.xz -UseBasicParsing
+  tar -xvzf endf.xz
+}
diff --git a/tools/ci/gha-install.ps1 b/tools/ci/gha-install.ps1
new file mode 100644
index 00000000000..600d8310ecc
--- /dev/null
+++ b/tools/ci/gha-install.ps1
@@ -0,0 +1,26 @@
+# Install VCPKG
+git clone https://github.com/microsoft/vcpkg.git "$Env:GITHUB_WORKSPACE\..\vcpkg"
+
+cd "$Env:GITHUB_WORKSPACE\..\vcpkg"
+.\bootstrap-vcpkg.bat
+
+[Environment]::SetEnvironmentVariable("VCPKG_ROOT", "$Env:GITHUB_WORKSPACE\..\vcpkg", [System.EnvironmentVariableTarget]::User)
+$Env:VCPKG_ROOT = "$Env:GITHUB_WORKSPACE\..\vcpkg"
+$Env:Path += ";$Env:VCPKG_ROOT"
+
+# Install HDF5
+vcpkg install hdf5:x64-windows-static
+
+# Go back to main directory for install
+cd "$Env:GITHUB_WORKSPACE"
+
+# Upgrade pip, pytest, numpy before doing anything else.
+pip install --upgrade pip
+pip install --upgrade pytest
+pip install --upgrade numpy
+
+# Build and install OpenMC executable
+python tools/ci/gha-install.py
+
+# Install Python API in editable mode
+pip install -e .[test,vtk,ci]
\ No newline at end of file
diff --git a/tools/ci/gha-install.py b/tools/ci/gha-install.py
index 1cc792f8d78..88f5b1d4441 100644
--- a/tools/ci/gha-install.py
+++ b/tools/ci/gha-install.py
@@ -1,4 +1,5 @@
 import os
+import sys
 import shutil
 import subprocess
 
@@ -10,7 +11,11 @@ def install(omp=False, mpi=False, phdf5=False, dagmc=False, libmesh=False):
     os.chdir('build')
 
     # Build in debug mode by default with support for MCPL
-    cmake_cmd = ['cmake', '-DCMAKE_BUILD_TYPE=Debug', '-DOPENMC_USE_MCPL=on']
+    if sys.platform == 'win32':
+        work_dir = os.environ.get('GITHUB_WORKSPACE')
+        cmake_cmd = ['cmake', '-DCMAKE_BUILD_TYPE=Release', '-DCMAKE_TOOLCHAIN_FILE='+work_dir+'\\..\\vcpkg\\scripts\\buildsystems\\vcpkg.cmake', '-DVCPKG_TARGET_TRIPLET=x64-windows-static']
+    else:
+        cmake_cmd = ['cmake', '-DCMAKE_BUILD_TYPE=Debug', '-DOPENMC_USE_MCPL=on']
 
     # Turn off OpenMP if specified
     if not omp:
@@ -41,14 +46,20 @@ def install(omp=False, mpi=False, phdf5=False, dagmc=False, libmesh=False):
         cmake_cmd.append('-DCMAKE_PREFIX_PATH=' + libmesh_path)
 
     # Build in coverage mode for coverage testing
-    cmake_cmd.append('-DOPENMC_ENABLE_COVERAGE=on')
+    if sys.platform != 'win32':
+        cmake_cmd.append('-DOPENMC_ENABLE_COVERAGE=on')
 
     # Build and install
     cmake_cmd.append('..')
     print(' '.join(cmake_cmd))
     subprocess.check_call(cmake_cmd)
-    subprocess.check_call(['make', '-j4'])
-    subprocess.check_call(['sudo', 'make', 'install'])
+
+    if sys.platform == 'win32':
+        subprocess.check_call(['cmake', '--build', '.', '--config=Release'])
+        subprocess.check_call(['cmake', '--install', '.', '--config=Release'])
+    else:
+        subprocess.check_call(['make', '-j4'])
+        subprocess.check_call(['sudo', 'make', 'install'])
 
 def main():
     # Convert Travis matrix environment variables into arguments for install()
diff --git a/tools/ci/gha-script.ps1 b/tools/ci/gha-script.ps1
new file mode 100644
index 00000000000..bd3f89b856b
--- /dev/null
+++ b/tools/ci/gha-script.ps1
@@ -0,0 +1,10 @@
+# Argument list
+$Env:args = ""
+
+# Check for event-based
+if ($Env:EVENT) {
+  $Env:args = $Env:args + " --event "
+}
+
+# Run regression and unit tests
+pytest --cov=openmc -v $Env:args tests
\ No newline at end of file