diff --git a/include/openmc/cross_sections.h b/include/openmc/cross_sections.h
index 2b0473becd..06140a6a8c 100644
--- a/include/openmc/cross_sections.h
+++ b/include/openmc/cross_sections.h
@@ -62,6 +62,11 @@ extern vector<Library> libraries;
 //! libraries
 void read_cross_sections_xml();
 
+//! Read cross sections file (either XML or multigroup H5) and populate data
+//! libraries
+//! \param[in] root node of the cross_sections.xml
+void read_cross_sections_xml(pugi::xml_node root);
+
 //! Load nuclide and thermal scattering data from HDF5 files
 //
 //! \param[in] nuc_temps Temperatures for each nuclide in [K]
diff --git a/include/openmc/geometry_aux.h b/include/openmc/geometry_aux.h
index b248d491ac..a4c506c31a 100644
--- a/include/openmc/geometry_aux.h
+++ b/include/openmc/geometry_aux.h
@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "openmc/vector.h"
+#include "openmc/xml_interface.h"
 
 namespace openmc {
 
@@ -19,8 +20,13 @@ extern std::unordered_map<int32_t, std::unordered_map<int32_t, int32_t>>
 extern std::unordered_map<int32_t, int32_t> universe_level_counts;
 } // namespace model
 
+//! Read geometry from XML file
 void read_geometry_xml();
 
+//! Read geometry from XML node
+//! \param[in]  root node of geometry XML element
+void read_geometry_xml(pugi::xml_node root);
+
 //==============================================================================
 //! Replace Universe, Lattice, and Material IDs with indices.
 //==============================================================================
diff --git a/include/openmc/material.h b/include/openmc/material.h
index b251a3ca85..81f4e1421c 100644
--- a/include/openmc/material.h
+++ b/include/openmc/material.h
@@ -221,6 +221,10 @@ double density_effect(const vector<double>& f, const vector<double>& e_b_sq,
 //! Read material data from materials.xml
 void read_materials_xml();
 
+//! Read material data XML node
+//! \param[in] root node of materials XML element
+void read_materials_xml(pugi::xml_node root);
+
 void free_memory_material();
 
 } // namespace openmc
diff --git a/include/openmc/plot.h b/include/openmc/plot.h
index 650b7e16a1..a415b17473 100644
--- a/include/openmc/plot.h
+++ b/include/openmc/plot.h
@@ -279,6 +279,10 @@ void voxel_finalize(hid_t dspace, hid_t dset, hid_t memspace);
 //! Read plot specifications from a plots.xml file
 void read_plots_xml();
 
+//! Read plot specifications from an XML Node
+//! \param[in] XML node containing plot info
+void read_plots_xml(pugi::xml_node root);
+
 //! Clear memory
 void free_memory_plot();
 
diff --git a/include/openmc/settings.h b/include/openmc/settings.h
index 1e061b235b..cd0ab477c4 100644
--- a/include/openmc/settings.h
+++ b/include/openmc/settings.h
@@ -127,9 +127,12 @@ extern double weight_survive;      //!< Survival weight after Russian roulette
 //==============================================================================
 
 //! Read settings from XML file
-//! \param[in] root XML node for <settings>
 void read_settings_xml();
 
+//! Read settings from XML node
+//! \param[in] root XML node for <settings>
+void read_settings_xml(pugi::xml_node root);
+
 void free_memory_settings();
 
 } // namespace openmc
diff --git a/include/openmc/tallies/tally.h b/include/openmc/tallies/tally.h
index 3cead91dc7..56a51370a8 100644
--- a/include/openmc/tallies/tally.h
+++ b/include/openmc/tallies/tally.h
@@ -48,10 +48,10 @@ public:
   void set_nuclides(const vector<std::string>& nuclides);
 
   //! returns vector of indices corresponding to the tally this is called on
-  const vector<int32_t>& filters() const { return filters_; } 
+  const vector<int32_t>& filters() const { return filters_; }
 
   //! \brief Returns the tally filter at index i
-  int32_t filters(int i) const { return filters_[i]; } 
+  int32_t filters(int i) const { return filters_[i]; }
 
   void set_filters(gsl::span<Filter*> filters);
 
@@ -178,6 +178,10 @@ extern double global_tally_leakage;
 //! Read tally specification from tallies.xml
 void read_tallies_xml();
 
+//! Read tally specification from an XML node
+//! \param[in] root node of tallies XML element
+void read_tallies_xml(pugi::xml_node root);
+
 //! \brief Accumulate the sum of the contributions from each history within the
 //! batch to a new random variable
 void accumulate_tallies();
diff --git a/src/cross_sections.cpp b/src/cross_sections.cpp
index afb0a1f36c..2094fd551f 100644
--- a/src/cross_sections.cpp
+++ b/src/cross_sections.cpp
@@ -91,8 +91,7 @@ Library::Library(pugi::xml_node node, const std::string& directory)
 // Non-member functions
 //==============================================================================
 
-void read_cross_sections_xml()
-{
+void read_cross_sections_xml() {
   pugi::xml_document doc;
   std::string filename = settings::path_input + "materials.xml";
   // Check if materials.xml exists
@@ -104,6 +103,11 @@ void read_cross_sections_xml()
 
   auto root = doc.document_element();
 
+  read_cross_sections_xml(root);
+}
+
+void read_cross_sections_xml(pugi::xml_node root)
+{
   // Find cross_sections.xml file -- the first place to look is the
   // materials.xml file. If no file is found there, then we check the
   // OPENMC_CROSS_SECTIONS environment variable
diff --git a/src/geometry_aux.cpp b/src/geometry_aux.cpp
index 2614719840..83e8494de6 100644
--- a/src/geometry_aux.cpp
+++ b/src/geometry_aux.cpp
@@ -40,8 +40,7 @@ void update_universe_cell_count(int32_t a, int32_t b)
   }
 }
 
-void read_geometry_xml()
-{
+void read_geometry_xml() {
   // Display output message
   write_message("Reading geometry XML file...", 5);
 
@@ -61,6 +60,11 @@ void read_geometry_xml()
   // Get root element
   pugi::xml_node root = doc.document_element();
 
+  read_geometry_xml(root);
+}
+
+void read_geometry_xml(pugi::xml_node root)
+{
   // Read surfaces, cells, lattice
   read_surfaces(root);
   read_cells(root);
diff --git a/src/initialize.cpp b/src/initialize.cpp
index aa353aa9cb..44f84034a7 100644
--- a/src/initialize.cpp
+++ b/src/initialize.cpp
@@ -14,6 +14,7 @@
 #include "openmc/constants.h"
 #include "openmc/cross_sections.h"
 #include "openmc/error.h"
+#include "openmc/file_utils.h"
 #include "openmc/geometry_aux.h"
 #include "openmc/hdf5_interface.h"
 #include "openmc/material.h"
@@ -291,10 +292,53 @@ int parse_command_line(int argc, char* argv[])
 
 void read_input_xml()
 {
-  read_settings_xml();
+
+  // search for a single model.xml file
+    // Check if settings.xml exists
+  std::string model_filename = settings::path_input + "model.xml";
+  bool use_model_file = file_exists(model_filename);
+  pugi::xml_node model_root;
+  if (use_model_file) {
+    write_message("Found model.xml file.");
+    pugi::xml_document doc;
+    auto result = doc.load_file(model_filename.c_str());
+    if (!result) {
+      fatal_error("Error processing model.xml file.");
+    }
+    auto model_root = doc.document_element();
+
+    auto other_inputs = {"materials.xml", "geometry.xml", "settings.xml", "tallies.xml", "plots.xml"};
+    for (const auto& input : other_inputs) {
+      if (file_exists(settings::path_input + input)) {
+        warning(fmt::format("A '{}' file is also present. This file will be ignored.", input));
+      }
+    }
+  } else {
+    write_message("No model.xml found. Reading separate XML inputs...");
+  }
+  if (use_model_file) {
+    if (!check_for_node(model_root, "settings")) {
+      fatal_error("No <settings> node present in the model.xml file.");
+    }
+    read_settings_xml(model_root.child("settings"));
+  } else {
+    read_settings_xml();
+  }
+
   read_cross_sections_xml();
-  read_materials_xml();
-  read_geometry_xml();
+  if (use_model_file) {
+    if (!check_for_node(model_root, "materials")) {
+      fatal_error("No <materials> node present in the model.xml file.");
+    }
+    read_materials_xml(model_root.child("materials"));
+    if (!check_for_node(model_root, "geometry")) {
+      fatal_error("No <geometry> node present in the model.xml_file.");
+    }
+    read_geometry_xml(model_root.child("geometry"));
+  } else {
+    read_materials_xml();
+    read_geometry_xml();
+  }
 
   // Final geometry setup and assign temperatures
   finalize_geometry();
@@ -302,14 +346,23 @@ void read_input_xml()
   // Finalize cross sections having assigned temperatures
   finalize_cross_sections();
 
-  read_tallies_xml();
+  if (use_model_file && check_for_node(model_root, "tallies")) {
+    read_tallies_xml(model_root.child("tallies"));
+  } else {
+    read_tallies_xml();
+  }
 
   // Initialize distribcell_filters
   prepare_distribcell();
 
   // Read the plots.xml regardless of plot mode in case plots are requested
   // via the API
-  read_plots_xml();
+  if (use_model_file) {
+    if (check_for_node(model_root, "plots"))
+      read_plots_xml(model_root.child("plots"));
+  } else {
+    read_plots_xml();
+  }
   if (settings::run_mode == RunMode::PLOTTING) {
     // Read plots.xml if it exists
     if (mpi::master && settings::verbosity >= 5)
diff --git a/src/material.cpp b/src/material.cpp
index 30dfa5ed50..f2e23aede2 100644
--- a/src/material.cpp
+++ b/src/material.cpp
@@ -1264,8 +1264,7 @@ double density_effect(const vector<double>& f, const vector<double>& e_b_sq,
   return delta - w_sq * (1.0 - beta_sq);
 }
 
-void read_materials_xml()
-{
+void read_materials_xml() {
   write_message("Reading materials XML file...", 5);
 
   pugi::xml_document doc;
@@ -1281,6 +1280,12 @@ void read_materials_xml()
 
   // Loop over XML material elements and populate the array.
   pugi::xml_node root = doc.document_element();
+
+  read_materials_xml(root);
+}
+
+void read_materials_xml(pugi::xml_node root)
+{
   for (pugi::xml_node material_node : root.children("material")) {
     model::materials.push_back(make_unique<Material>(material_node));
   }
diff --git a/src/plot.cpp b/src/plot.cpp
index b012ed1311..e28543cdff 100644
--- a/src/plot.cpp
+++ b/src/plot.cpp
@@ -124,8 +124,7 @@ extern "C" int openmc_plot_geometry()
   return 0;
 }
 
-void read_plots_xml()
-{
+void read_plots_xml() {
   // Check if plots.xml exists; this is only necessary when the plot runmode is
   // initiated. Otherwise, we want to read plots.xml because it may be called
   // later via the API. In that case, its ok for a plots.xml to not exist
@@ -141,6 +140,10 @@ void read_plots_xml()
   doc.load_file(filename.c_str());
 
   pugi::xml_node root = doc.document_element();
+}
+
+void read_plots_xml(pugi::xml_node root)
+{
   for (auto node : root.children("plot")) {
     model::plots.emplace_back(node);
     model::plot_map[model::plots.back().id_] = model::plots.size() - 1;
diff --git a/src/settings.cpp b/src/settings.cpp
index eb0d4936c7..710fb28101 100644
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -211,13 +211,11 @@ void get_run_parameters(pugi::xml_node node_base)
   }
 }
 
-void read_settings_xml()
-{
+void read_settings_xml() {
   using namespace settings;
   using namespace pugi;
-
   // Check if settings.xml exists
-  std::string filename = path_input + "settings.xml";
+  std::string filename = settings::path_input + "settings.xml";
   if (!file_exists(filename)) {
     if (run_mode != RunMode::PLOTTING) {
       fatal_error(
@@ -245,6 +243,14 @@ void read_settings_xml()
   // Get root element
   xml_node root = doc.document_element();
 
+  read_settings_xml(root);
+}
+
+void read_settings_xml(pugi::xml_node root)
+{
+  using namespace settings;
+  using namespace pugi;
+
   // Verbosity
   if (check_for_node(root, "verbosity")) {
     verbosity = std::stoi(get_node_value(root, "verbosity"));
diff --git a/src/tallies/tally.cpp b/src/tallies/tally.cpp
index 51194684ae..1c1f274d79 100644
--- a/src/tallies/tally.cpp
+++ b/src/tallies/tally.cpp
@@ -705,8 +705,7 @@ std::string Tally::nuclide_name(int nuclide_idx) const
 // Non-member functions
 //==============================================================================
 
-void read_tallies_xml()
-{
+void read_tallies_xml() {
   // Check if tallies.xml exists. If not, just return since it is optional
   std::string filename = settings::path_input + "tallies.xml";
   if (!file_exists(filename))
@@ -719,6 +718,11 @@ void read_tallies_xml()
   doc.load_file(filename.c_str());
   pugi::xml_node root = doc.document_element();
 
+  read_tallies_xml(root);
+}
+
+void read_tallies_xml(pugi::xml_node root)
+{
   // Check for <assume_separate> setting
   if (check_for_node(root, "assume_separate")) {
     settings::assume_separate = get_node_value_bool(root, "assume_separate");