diff --git a/src/fortuno_mpi/mpicmdapp.f90 b/src/fortuno_mpi/mpicmdapp.f90
index 911bcfa..986eb44 100644
--- a/src/fortuno_mpi/mpicmdapp.f90
+++ b/src/fortuno_mpi/mpicmdapp.f90
@@ -4,6 +4,7 @@
 
 !> Contains the command line app for driving mpi tests
 module fortuno_mpi_mpicmdapp
+  use mpi_f08, only : MPI_Comm
   use fortuno, only : cmd_app, test_list
   use fortuno_mpi_mpidriver, only : init_mpi_driver, mpi_driver
   use fortuno_mpi_mpienv, only : init_mpi_env, final_mpi_env, mpi_env
@@ -24,21 +25,24 @@ module fortuno_mpi_mpicmdapp
   !!
   !! Note: This routine stops the code during execution and never returns.
   !!
-  subroutine execute_mpi_cmd_app(tests)
+  subroutine execute_mpi_cmd_app(tests, comm)
 
     !> Items to be considered by the app
     type(test_list), intent(in) :: tests
 
+    !> Optional MPI communicator provided by caller
+    type(MPI_Comm), optional, intent(in) :: comm
+
     integer :: exitcode
 
-    call run_mpi_cmd_app(tests, exitcode)
+    call run_mpi_cmd_app(tests, exitcode, comm)
     stop exitcode, quiet=.true.
 
   end subroutine execute_mpi_cmd_app
 
 
-  !> Sets up and runs the mpi command line up
-  subroutine run_mpi_cmd_app(tests, exitcode)
+  !> Sets up and runs the mpi command line
+  subroutine run_mpi_cmd_app(tests, exitcode, comm)
 
     !> Items to be considered by the app
     type(test_list), intent(in) :: tests
@@ -46,10 +50,13 @@ subroutine run_mpi_cmd_app(tests, exitcode)
     !> Exit code
     integer, intent(out) :: exitcode
 
+    !> Optional MPI communicator provided by caller
+    type(MPI_Comm), optional, intent(in) :: comm
+
     type(mpi_cmd_app) :: app
     type(mpi_env) :: mpienv
 
-    call init_mpi_env(mpienv)
+    call init_mpi_env(mpienv, comm)
     call init_mpi_cmd_app(app, mpienv)
     call app%run(tests, exitcode)
     call final_mpi_env(mpienv)
diff --git a/src/fortuno_mpi/mpienv.f90 b/src/fortuno_mpi/mpienv.f90
index 36d15d0..4007952 100644
--- a/src/fortuno_mpi/mpienv.f90
+++ b/src/fortuno_mpi/mpienv.f90
@@ -34,16 +34,24 @@ module fortuno_mpi_mpienv
 contains
 
   !> Initializes the MPI environment
-  subroutine init_mpi_env(this)
+  subroutine init_mpi_env(this, comm)
 
     !> Instance
     type(mpi_env), intent(out) :: this
 
+    !> Optional MPI communicator provided by caller
+    type(MPI_Comm), optional, intent(in) :: comm
+
     integer :: ierror
 
-    call MPI_Init(ierror)
-    if (ierror /= 0) error stop "MPI_Init failed in init_mpi_env"
-    this%comm = MPI_COMM_WORLD
+    if (present(comm)) then
+      this%comm = comm
+    else
+      call MPI_Init(ierror)
+      if (ierror /= 0) error stop "MPI_Init failed in init_mpi_env"
+      this%comm = MPI_COMM_WORLD
+    endif
+
     call MPI_Comm_size(this%comm, this%nranks, ierror)
     if (ierror /= 0) error stop "MPI_Comm_size failed in init_mpi_env"
     call MPI_Comm_rank(this%comm, this%rank, ierror)