diff --git a/docs/dev/changelog/writer-mpi-comm.md b/docs/dev/changelog/writer-mpi-comm.md
new file mode 100644
index 0000000000000000000000000000000000000000..32b1e6e6c1116d44cbe322c0d267a7641f5ba366
--- /dev/null
+++ b/docs/dev/changelog/writer-mpi-comm.md
@@ -0,0 +1,3 @@
+## Support changing MPI_Comm for DataSetWriter
+
+The DataSetWriter now allows an MPI_Comm to be passed in, with the default being MPI_COMM_WORLD.
diff --git a/fides/CMakeLists.txt b/fides/CMakeLists.txt
index e7400102f349561d57df607b2476bdebdd5be6f9..2bb65ba07f425e6985c6ba8b0f4d3c94aaba6ff5 100644
--- a/fides/CMakeLists.txt
+++ b/fides/CMakeLists.txt
@@ -48,7 +48,7 @@ endif()
 
 fides_generate_export_header(fides)
 
-target_compile_definitions(fides PRIVATE ${MPI_DEFS} ${ADIOS_DEFS})
+target_compile_definitions(fides PUBLIC ${MPI_DEFS} PRIVATE ${ADIOS_DEFS})
 set(VTKM_LIBS vtkm::cont vtkm::filter_clean_grid)
 target_link_libraries(fides PUBLIC ${VTKM_LIBS} adios2::adios2 PRIVATE
   fides_rapidjson)
diff --git a/fides/DataSetWriter.cxx b/fides/DataSetWriter.cxx
index 9f72a172e5f96c53ab6038361003a54b91201982..f583a88bc03401b98cb7bf794bd66046e3972b92 100644
--- a/fides/DataSetWriter.cxx
+++ b/fides/DataSetWriter.cxx
@@ -483,15 +483,17 @@ public:
     : DataSets(dataSets)
     , OutputFileName(fname)
 #ifdef FIDES_USE_MPI
-    , Adios(MPI_COMM_WORLD)
+    // leaving in this FIDES_USE_MPI check, as you could still use this ctor even if building with MPI
+    , Comm(MPI_COMM_WORLD)
+    , Adios(Comm)
 #else
     , Adios()
 #endif
     , FieldsToWriteSet(false)
   {
 #ifdef FIDES_USE_MPI
-    MPI_Comm_rank(MPI_COMM_WORLD, &this->Rank);
-    MPI_Comm_size(MPI_COMM_WORLD, &this->NumRanks);
+    MPI_Comm_rank(this->Comm, &this->Rank);
+    MPI_Comm_size(this->Comm, &this->NumRanks);
 #endif
 
     this->IO = this->Adios.DeclareIO(outputMode);
@@ -500,6 +502,28 @@ public:
                                  (appendMode ? adios2::Mode::Append : adios2::Mode::Write));
   }
 
+#ifdef FIDES_USE_MPI
+  GenericWriter(const vtkm::cont::PartitionedDataSet& dataSets,
+                const std::string& fname,
+                const std::string& outputMode,
+                MPI_Comm comm,
+                const bool& appendMode = false)
+    : DataSets(dataSets)
+    , OutputFileName(fname)
+    , Comm(comm)
+    , Adios(comm)
+    , FieldsToWriteSet(false)
+  {
+    MPI_Comm_rank(this->Comm, &this->Rank);
+    MPI_Comm_size(this->Comm, &this->NumRanks);
+
+    this->IO = this->Adios.DeclareIO(outputMode);
+    this->IO.SetEngine(outputMode);
+    this->Engine = this->IO.Open(this->OutputFileName,
+                                 (appendMode ? adios2::Mode::Append : adios2::Mode::Write));
+  }
+#endif
+
   void Close()
   {
     this->Engine.Close();
@@ -751,7 +775,7 @@ protected:
 
 #ifdef FIDES_USE_MPI
     MPI_Allreduce(
-      MPI_IN_PLACE, this->DataSetsPerRank.data(), this->NumRanks, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
+      MPI_IN_PLACE, this->DataSetsPerRank.data(), this->NumRanks, MPI_INT, MPI_SUM, this->Comm);
 #endif
 
     int tot = std::accumulate(this->DataSetsPerRank.begin(), this->DataSetsPerRank.end(), 0);
@@ -775,8 +799,8 @@ protected:
     }
 
 #ifdef FIDES_USE_MPI
-    MPI_Allreduce(MPI_IN_PLACE, numPoints.data(), this->NumRanks, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
-    MPI_Allreduce(MPI_IN_PLACE, numCells.data(), this->NumRanks, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
+    MPI_Allreduce(MPI_IN_PLACE, numPoints.data(), this->NumRanks, MPI_INT, MPI_SUM, this->Comm);
+    MPI_Allreduce(MPI_IN_PLACE, numCells.data(), this->NumRanks, MPI_INT, MPI_SUM, this->Comm);
 #endif
 
     tot = std::accumulate(numPoints.begin(), numPoints.end(), 0);
@@ -799,6 +823,10 @@ protected:
 
   vtkm::cont::PartitionedDataSet DataSets;
   std::string OutputFileName;
+
+#ifdef FIDES_USE_MPI
+  MPI_Comm Comm;
+#endif
   adios2::ADIOS Adios;
   adios2::IO IO;
   adios2::Engine Engine;
@@ -836,6 +864,17 @@ public:
   {
   }
 
+#ifdef FIDES_USE_MPI
+  UniformDataSetWriter(const vtkm::cont::PartitionedDataSet& dataSets,
+                       const std::string& fname,
+                       const std::string& outputMode,
+                       MPI_Comm comm,
+                       const bool& appendMode = false)
+    : GenericWriter(dataSets, fname, outputMode, comm, appendMode)
+  {
+  }
+#endif
+
   void DefineDataModelVariables() override
   {
     std::vector<std::size_t> shape = { 3 * this->TotalNumberOfDataSets };
@@ -919,6 +958,17 @@ public:
   {
   }
 
+#ifdef FIDES_USE_MPI
+  RectilinearDataSetWriter(const vtkm::cont::PartitionedDataSet& dataSets,
+                           const std::string& fname,
+                           const std::string& outputMode,
+                           MPI_Comm comm,
+                           const bool& appendMode = false)
+    : GenericWriter(dataSets, fname, outputMode, comm, appendMode)
+  {
+  }
+#endif
+
   void DefineDataModelVariables() override
   {
     std::vector<std::size_t> shape, offset, size;
@@ -1029,7 +1079,7 @@ protected:
 
 #ifdef FIDES_USE_MPI
     MPI_Allreduce(
-      MPI_IN_PLACE, numCoordinates.data(), this->NumRanks * 3, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
+      MPI_IN_PLACE, numCoordinates.data(), this->NumRanks * 3, MPI_INT, MPI_SUM, this->Comm);
 #endif
     this->TotalNumberOfXCoords = 0;
     this->TotalNumberOfYCoords = 0;
@@ -1077,6 +1127,17 @@ public:
   {
   }
 
+#ifdef FIDES_USE_MPI
+  UnstructuredSingleTypeDataSetWriter(const vtkm::cont::PartitionedDataSet& dataSets,
+                                      const std::string& fname,
+                                      const std::string& outputMode,
+                                      MPI_Comm comm,
+                                      const bool& appendMode = false)
+    : GenericWriter(dataSets, fname, outputMode, comm, appendMode)
+  {
+  }
+#endif
+
   void DefineDataModelVariables() override
   {
     std::vector<std::size_t> shape, offset, size;
@@ -1170,11 +1231,10 @@ protected:
 
 #ifdef FIDES_USE_MPI
     MPI_Allreduce(
-      MPI_IN_PLACE, numCoordinates.data(), this->NumRanks, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
-    MPI_Allreduce(MPI_IN_PLACE, numCells.data(), this->NumRanks, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
-    MPI_Allreduce(
-      MPI_IN_PLACE, numPtsInCell.data(), this->NumRanks, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
-    MPI_Allreduce(MPI_IN_PLACE, cellShape.data(), this->NumRanks, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
+      MPI_IN_PLACE, numCoordinates.data(), this->NumRanks, MPI_INT, MPI_SUM, this->Comm);
+    MPI_Allreduce(MPI_IN_PLACE, numCells.data(), this->NumRanks, MPI_INT, MPI_SUM, this->Comm);
+    MPI_Allreduce(MPI_IN_PLACE, numPtsInCell.data(), this->NumRanks, MPI_INT, MPI_SUM, this->Comm);
+    MPI_Allreduce(MPI_IN_PLACE, cellShape.data(), this->NumRanks, MPI_INT, MPI_SUM, this->Comm);
 #endif
 
     for (int i = 0; i < this->NumRanks; i++)
@@ -1226,6 +1286,23 @@ public:
                                     const std::string& outputMode,
                                     const bool& appendMode = false)
     : GenericWriter(dataSets, fname, outputMode, appendMode)
+  {
+    this->ValidatePartitionTypes(dataSets);
+  }
+
+#ifdef FIDES_USE_MPI
+  UnstructuredExplicitDataSetWriter(const vtkm::cont::PartitionedDataSet& dataSets,
+                                    const std::string& fname,
+                                    const std::string& outputMode,
+                                    MPI_Comm comm,
+                                    const bool& appendMode = false)
+    : GenericWriter(dataSets, fname, outputMode, comm, appendMode)
+  {
+    this->ValidatePartitionTypes(dataSets);
+  }
+#endif
+
+  void ValidatePartitionTypes(const vtkm::cont::PartitionedDataSet& dataSets)
   {
     // Validate that every partition has the same type:
     for (auto const& ds : dataSets)
@@ -1343,9 +1420,9 @@ protected:
     numConns[this->Rank] = this->NumConns;
 #ifdef FIDES_USE_MPI
     MPI_Allreduce(
-      MPI_IN_PLACE, numCoordinates.data(), this->NumRanks, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
-    MPI_Allreduce(MPI_IN_PLACE, numCells.data(), this->NumRanks, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
-    MPI_Allreduce(MPI_IN_PLACE, numConns.data(), this->NumRanks, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
+      MPI_IN_PLACE, numCoordinates.data(), this->NumRanks, MPI_INT, MPI_SUM, this->Comm);
+    MPI_Allreduce(MPI_IN_PLACE, numCells.data(), this->NumRanks, MPI_INT, MPI_SUM, this->Comm);
+    MPI_Allreduce(MPI_IN_PLACE, numConns.data(), this->NumRanks, MPI_INT, MPI_SUM, this->Comm);
 #endif
 
     for (int i = 0; i < this->NumRanks; i++)
@@ -1386,6 +1463,15 @@ DataSetWriter::DataSetWriter(const std::string& outputFile)
 {
 }
 
+#ifdef FIDES_USE_MPI
+DataSetWriter::DataSetWriter(const std::string& outputFile, MPI_Comm comm)
+  : OutputFile(outputFile)
+  , WriteFieldSet(false)
+  , Comm(comm)
+{
+}
+#endif
+
 unsigned char DataSetWriter::GetDataSetType(const vtkm::cont::DataSet& ds)
 {
   using UniformCoordType = vtkm::cont::ArrayHandleUniformPointCoordinates;
@@ -1428,8 +1514,8 @@ void DataSetWriter::SetDataSetType(const vtkm::cont::PartitionedDataSet& dataSet
 {
   int rank = 0, numRanks = 1;
 #ifdef FIDES_USE_MPI
-  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
-  MPI_Comm_size(MPI_COMM_WORLD, &numRanks);
+  MPI_Comm_rank(this->Comm, &rank);
+  MPI_Comm_size(this->Comm, &numRanks);
 #endif
 
   //Make sure all the datasets are the same.
@@ -1457,7 +1543,7 @@ void DataSetWriter::SetDataSetType(const vtkm::cont::PartitionedDataSet& dataSet
   allDataSetTypes[rank] = dataSetType;
 #ifdef FIDES_USE_MPI
   MPI_Allreduce(
-    MPI_IN_PLACE, allDataSetTypes.data(), numRanks, MPI_UNSIGNED_CHAR, MPI_BOR, MPI_COMM_WORLD);
+    MPI_IN_PLACE, allDataSetTypes.data(), numRanks, MPI_UNSIGNED_CHAR, MPI_BOR, this->Comm);
 #endif
 
   //If we OR these values all together, we will get the global dataset type.
@@ -1492,7 +1578,11 @@ void DataSetWriter::Write(const vtkm::cont::PartitionedDataSet& dataSets,
   }
   else if (this->DataSetType == DATASET_TYPE_UNIFORM)
   {
+#ifdef FIDES_USE_MPI
+    UniformDataSetWriter writeImpl(dataSets, this->OutputFile, outputMode, this->Comm);
+#else
     UniformDataSetWriter writeImpl(dataSets, this->OutputFile, outputMode);
+#endif
     if (this->WriteFieldSet)
       writeImpl.SetWriteFields(this->FieldsToWrite);
 
@@ -1501,7 +1591,11 @@ void DataSetWriter::Write(const vtkm::cont::PartitionedDataSet& dataSets,
   }
   else if (this->DataSetType == DATASET_TYPE_RECTILINEAR)
   {
+#ifdef FIDES_USE_MPI
+    RectilinearDataSetWriter writeImpl(dataSets, this->OutputFile, outputMode, this->Comm);
+#else
     RectilinearDataSetWriter writeImpl(dataSets, this->OutputFile, outputMode);
+#endif
     if (this->WriteFieldSet)
       writeImpl.SetWriteFields(this->FieldsToWrite);
     writeImpl.Write();
@@ -1509,7 +1603,12 @@ void DataSetWriter::Write(const vtkm::cont::PartitionedDataSet& dataSets,
   }
   else if (this->DataSetType == DATASET_TYPE_UNSTRUCTURED_SINGLE)
   {
+#ifdef FIDES_USE_MPI
+    UnstructuredSingleTypeDataSetWriter writeImpl(
+      dataSets, this->OutputFile, outputMode, this->Comm);
+#else
     UnstructuredSingleTypeDataSetWriter writeImpl(dataSets, this->OutputFile, outputMode);
+#endif
     if (this->WriteFieldSet)
       writeImpl.SetWriteFields(this->FieldsToWrite);
     writeImpl.Write();
@@ -1517,7 +1616,11 @@ void DataSetWriter::Write(const vtkm::cont::PartitionedDataSet& dataSets,
   }
   else if (this->DataSetType == DATASET_TYPE_UNSTRUCTURED)
   {
+#ifdef FIDES_USE_MPI
+    UnstructuredExplicitDataSetWriter writeImpl(dataSets, this->OutputFile, outputMode, this->Comm);
+#else
     UnstructuredExplicitDataSetWriter writeImpl(dataSets, this->OutputFile, outputMode);
+#endif
     if (this->WriteFieldSet)
       writeImpl.SetWriteFields(this->FieldsToWrite);
     writeImpl.Write();
@@ -1536,6 +1639,15 @@ DataSetAppendWriter::DataSetAppendWriter(const std::string& outputFile)
 {
 }
 
+#ifdef FIDES_USE_MPI
+DataSetAppendWriter::DataSetAppendWriter(const std::string& outputFile, MPI_Comm comm)
+  : DataSetWriter(outputFile, comm)
+  , IsInitialized(false)
+  , Writer(nullptr)
+{
+}
+#endif
+
 void DataSetAppendWriter::Write(const vtkm::cont::PartitionedDataSet& dataSets,
                                 const std::string& outputMode)
 {
@@ -1569,23 +1681,43 @@ void DataSetAppendWriter::Initialize(const vtkm::cont::PartitionedDataSet& dataS
   this->SetDataSetType(dataSets);
   if (this->DataSetType == DATASET_TYPE_UNIFORM)
   {
+#ifdef FIDES_USE_MPI
+    this->Writer.reset(new DataSetWriter::UniformDataSetWriter(
+      dataSets, this->OutputFile, outputMode, this->Comm, true));
+#else
     this->Writer.reset(
       new DataSetWriter::UniformDataSetWriter(dataSets, this->OutputFile, outputMode, true));
+#endif
   }
   else if (this->DataSetType == DATASET_TYPE_RECTILINEAR)
   {
+#ifdef FIDES_USE_MPI
+    this->Writer.reset(new DataSetWriter::RectilinearDataSetWriter(
+      dataSets, this->OutputFile, outputMode, this->Comm, true));
+#else
     this->Writer.reset(
       new DataSetWriter::RectilinearDataSetWriter(dataSets, this->OutputFile, outputMode, true));
+#endif
   }
   else if (this->DataSetType == DATASET_TYPE_UNSTRUCTURED_SINGLE)
   {
+#ifdef FIDES_USE_MPI
+    this->Writer.reset(new UnstructuredSingleTypeDataSetWriter(
+      dataSets, this->OutputFile, outputMode, this->Comm, true));
+#else
     this->Writer.reset(
       new UnstructuredSingleTypeDataSetWriter(dataSets, this->OutputFile, outputMode, true));
+#endif
   }
   else if (this->DataSetType == DATASET_TYPE_UNSTRUCTURED)
   {
+#ifdef FIDES_USE_MPI
+    this->Writer.reset(new UnstructuredExplicitDataSetWriter(
+      dataSets, this->OutputFile, outputMode, this->Comm, true));
+#else
     this->Writer.reset(
       new UnstructuredExplicitDataSetWriter(dataSets, this->OutputFile, outputMode, true));
+#endif
   }
   else
   {
diff --git a/fides/DataSetWriter.h b/fides/DataSetWriter.h
index 69afbf360a2aff50f73599c9c672100eb34a734e..ce0758dd3cdb96a64c570c1a140e778cc72c1e5a 100644
--- a/fides/DataSetWriter.h
+++ b/fides/DataSetWriter.h
@@ -24,6 +24,10 @@
 
 #include "fides_export.h"
 
+#ifdef FIDES_USE_MPI
+#include <mpi.h>
+#endif
+
 namespace fides
 {
 namespace io
@@ -38,6 +42,9 @@ class FIDES_EXPORT DataSetWriter
 {
 public:
   DataSetWriter(const std::string& outputFile);
+#ifdef FIDES_USE_MPI
+  DataSetWriter(const std::string& outputFile, MPI_Comm comm);
+#endif
   ~DataSetWriter() = default;
 
   void Write(const vtkm::cont::PartitionedDataSet& dataSets, const std::string& outputMode);
@@ -72,12 +79,18 @@ protected:
   unsigned char DataSetType;
   std::set<std::string> FieldsToWrite;
   bool WriteFieldSet;
+#ifdef FIDES_USE_MPI
+  MPI_Comm Comm = MPI_COMM_WORLD;
+#endif
 };
 
 class FIDES_EXPORT DataSetAppendWriter : public DataSetWriter
 {
 public:
   DataSetAppendWriter(const std::string& outputFile);
+#ifdef FIDES_USE_MPI
+  DataSetAppendWriter(const std::string& outputFile, MPI_Comm comm);
+#endif
   ~DataSetAppendWriter() = default;
 
   void Write(const vtkm::cont::PartitionedDataSet& dataSets, const std::string& outputMode);