diff --git a/flang/include/flang/Parser/dump-parse-tree.h b/flang/include/flang/Parser/dump-parse-tree.h
index 06c168a5de612..477d391277ee2 100644
--- a/flang/include/flang/Parser/dump-parse-tree.h
+++ b/flang/include/flang/Parser/dump-parse-tree.h
@@ -542,6 +542,7 @@ class ParseTreeDumper {
   NODE_ENUM(OmpOrderModifier, Kind)
   NODE(parser, OmpProcBindClause)
   NODE_ENUM(OmpProcBindClause, Type)
+  NODE_ENUM(OmpReductionClause, ReductionModifier)
   NODE(parser, OmpReductionClause)
   NODE(parser, OmpInReductionClause)
   NODE(parser, OmpReductionCombiner)
diff --git a/flang/include/flang/Parser/parse-tree.h b/flang/include/flang/Parser/parse-tree.h
index 26b2e5f4e34b0..9e3c4e0e67c3b 100644
--- a/flang/include/flang/Parser/parse-tree.h
+++ b/flang/include/flang/Parser/parse-tree.h
@@ -3551,7 +3551,10 @@ struct OmpReductionOperator {
 //                                         variable-name-list)
 struct OmpReductionClause {
   TUPLE_CLASS_BOILERPLATE(OmpReductionClause);
-  std::tuple<OmpReductionOperator, OmpObjectList> t;
+  ENUM_CLASS(ReductionModifier, Inscan, Task, Default)
+  std::tuple<std::optional<ReductionModifier>, OmpReductionOperator,
+      OmpObjectList>
+      t;
 };
 
 // OMP 5.0 2.19.5.6 in_reduction-clause -> IN_REDUCTION (reduction-identifier:
diff --git a/flang/lib/Lower/OpenMP/Clauses.cpp b/flang/lib/Lower/OpenMP/Clauses.cpp
index 40da71c8b55f8..97337cfc08c72 100644
--- a/flang/lib/Lower/OpenMP/Clauses.cpp
+++ b/flang/lib/Lower/OpenMP/Clauses.cpp
@@ -1005,12 +1005,28 @@ ProcBind make(const parser::OmpClause::ProcBind &inp,
 Reduction make(const parser::OmpClause::Reduction &inp,
                semantics::SemanticsContext &semaCtx) {
   // inp.v -> parser::OmpReductionClause
-  auto &t0 = std::get<parser::OmpReductionOperator>(inp.v.t);
-  auto &t1 = std::get<parser::OmpObjectList>(inp.v.t);
+  using wrapped = parser::OmpReductionClause;
+
+  CLAUSET_ENUM_CONVERT( //
+      convert, wrapped::ReductionModifier, Reduction::ReductionModifier,
+      // clang-format off
+      MS(Inscan,  Inscan)
+      MS(Task,    Task)
+      MS(Default, Default)
+      // clang-format on
+  );
+
+  auto &t0 =
+      std::get<std::optional<parser::OmpReductionClause::ReductionModifier>>(
+          inp.v.t);
+  auto &t1 = std::get<parser::OmpReductionOperator>(inp.v.t);
+  auto &t2 = std::get<parser::OmpObjectList>(inp.v.t);
   return Reduction{
-      {/*ReductionIdentifiers=*/{makeReductionOperator(t0, semaCtx)},
-       /*ReductionModifier=*/std::nullopt,
-       /*List=*/makeObjects(t1, semaCtx)}};
+      {/*ReductionModifier=*/t0
+           ? std::make_optional<Reduction::ReductionModifier>(convert(*t0))
+           : std::nullopt,
+       /*ReductionIdentifiers=*/{makeReductionOperator(t1, semaCtx)},
+       /*List=*/makeObjects(t2, semaCtx)}};
 }
 
 // Relaxed: empty
diff --git a/flang/lib/Lower/OpenMP/ReductionProcessor.cpp b/flang/lib/Lower/OpenMP/ReductionProcessor.cpp
index c1c94119fd908..4323917c1f62e 100644
--- a/flang/lib/Lower/OpenMP/ReductionProcessor.cpp
+++ b/flang/lib/Lower/OpenMP/ReductionProcessor.cpp
@@ -496,6 +496,11 @@ void ReductionProcessor::addDeclareReduction(
     llvm::SmallVectorImpl<const Fortran::semantics::Symbol *>
         *reductionSymbols) {
   fir::FirOpBuilder &firOpBuilder = converter.getFirOpBuilder();
+
+  if (std::get<std::optional<omp::clause::Reduction::ReductionModifier>>(
+          reduction.t))
+    TODO(currentLocation, "Reduction modifiers are not supported");
+
   mlir::omp::DeclareReductionOp decl;
   const auto &redOperatorList{
       std::get<omp::clause::Reduction::ReductionIdentifiers>(reduction.t)};
diff --git a/flang/lib/Parser/openmp-parsers.cpp b/flang/lib/Parser/openmp-parsers.cpp
index bba1be27158ce..eae4784169146 100644
--- a/flang/lib/Parser/openmp-parsers.cpp
+++ b/flang/lib/Parser/openmp-parsers.cpp
@@ -136,6 +136,11 @@ TYPE_PARSER(construct<OmpReductionOperator>(Parser<DefinedOperator>{}) ||
     construct<OmpReductionOperator>(Parser<ProcedureDesignator>{}))
 
 TYPE_PARSER(construct<OmpReductionClause>(
+    maybe(
+        ("INSCAN" >> pure(OmpReductionClause::ReductionModifier::Inscan) ||
+            "TASK" >> pure(OmpReductionClause::ReductionModifier::Task) ||
+            "DEFAULT" >> pure(OmpReductionClause::ReductionModifier::Default)) /
+        ","),
     Parser<OmpReductionOperator>{} / ":", Parser<OmpObjectList>{}))
 
 // OMP 5.0 2.19.5.6 IN_REDUCTION (reduction-identifier: variable-name-list)
diff --git a/flang/lib/Parser/unparse.cpp b/flang/lib/Parser/unparse.cpp
index c06458833f072..3398b395f198f 100644
--- a/flang/lib/Parser/unparse.cpp
+++ b/flang/lib/Parser/unparse.cpp
@@ -2090,6 +2090,8 @@ class UnparseVisitor {
     Walk(":", x.step);
   }
   void Unparse(const OmpReductionClause &x) {
+    Walk(std::get<std::optional<OmpReductionClause::ReductionModifier>>(x.t),
+        ",");
     Walk(std::get<OmpReductionOperator>(x.t));
     Put(":");
     Walk(std::get<OmpObjectList>(x.t));
@@ -2727,6 +2729,8 @@ class UnparseVisitor {
   WALK_NESTED_ENUM(OmpScheduleClause, ScheduleType) // OMP schedule-type
   WALK_NESTED_ENUM(OmpDeviceClause, DeviceModifier) // OMP device modifier
   WALK_NESTED_ENUM(OmpDeviceTypeClause, Type) // OMP DEVICE_TYPE
+  WALK_NESTED_ENUM(
+      OmpReductionClause, ReductionModifier) // OMP reduction-modifier
   WALK_NESTED_ENUM(OmpIfClause, DirectiveNameModifier) // OMP directive-modifier
   WALK_NESTED_ENUM(OmpCancelType, Type) // OMP cancel-type
   WALK_NESTED_ENUM(OmpOrderClause, Type) // OMP order-type
diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index bf4debee1df34..e85d8d1f7ab53 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -2289,7 +2289,7 @@ void OmpStructureChecker::Enter(const parser::OmpClause::Reduction &x) {
 bool OmpStructureChecker::CheckReductionOperators(
     const parser::OmpClause::Reduction &x) {
 
-  const auto &definedOp{std::get<0>(x.v.t)};
+  const auto &definedOp{std::get<parser::OmpReductionOperator>(x.v.t)};
   bool ok = false;
   common::visit(
       common::visitors{
diff --git a/flang/test/Lower/OpenMP/Todo/reduction-modifiers.f90 b/flang/test/Lower/OpenMP/Todo/reduction-modifiers.f90
new file mode 100644
index 0000000000000..5e566466492ce
--- /dev/null
+++ b/flang/test/Lower/OpenMP/Todo/reduction-modifiers.f90
@@ -0,0 +1,13 @@
+! RUN: %not_todo_cmd bbc -emit-fir -fopenmp -o - %s 2>&1 | FileCheck %s
+! RUN: %not_todo_cmd %flang_fc1 -emit-fir -fopenmp -o - %s 2>&1 | FileCheck %s
+
+! CHECK: not yet implemented: Reduction modifiers are not supported
+
+subroutine foo()
+  integer :: i, j
+  j = 0
+  !$omp do reduction (inscan, *: j)
+  do i = 1, 10
+    j = j + 1
+  end do
+end subroutine
diff --git a/flang/test/Parser/OpenMP/reduction-modifier.f90 b/flang/test/Parser/OpenMP/reduction-modifier.f90
new file mode 100644
index 0000000000000..d46aa70959592
--- /dev/null
+++ b/flang/test/Parser/OpenMP/reduction-modifier.f90
@@ -0,0 +1,20 @@
+! RUN: %flang_fc1 -fdebug-unparse-no-sema -fopenmp %s | FileCheck --ignore-case %s
+! RUN: %flang_fc1 -fdebug-dump-parse-tree-no-sema -fopenmp %s | FileCheck --check-prefix="PARSE-TREE" %s
+
+subroutine foo()
+  integer :: i, j
+  j = 0
+! CHECK: !$OMP DO  REDUCTION(TASK,*:j)
+! PARSE-TREE: | | ExecutionPartConstruct -> ExecutableConstruct -> OpenMPConstruct -> OpenMPLoopConstruct
+! PARSE-TREE: | | | OmpBeginLoopDirective
+! PARSE-TREE: | | | | OmpLoopDirective -> llvm::omp::Directive = do
+! PARSE-TREE: | | | | OmpClauseList -> OmpClause -> Reduction -> OmpReductionClause
+! PARSE-TREE: | | | | | ReductionModifier = Task
+! PARSE-TREE: | | | | | OmpReductionOperator -> DefinedOperator -> IntrinsicOperator = Multiply
+! PARSE-TREE: | | | | | OmpObjectList -> OmpObject -> Designator -> DataRef -> Name = 'j
+  !$omp do reduction (task, *: j)
+  do i = 1, 10
+    j = j + 1
+  end do
+  !$omp end do
+end
diff --git a/llvm/include/llvm/Frontend/OpenMP/ClauseT.h b/llvm/include/llvm/Frontend/OpenMP/ClauseT.h
index 6ce972adcf0fb..daef02bcfc9a3 100644
--- a/llvm/include/llvm/Frontend/OpenMP/ClauseT.h
+++ b/llvm/include/llvm/Frontend/OpenMP/ClauseT.h
@@ -949,7 +949,7 @@ struct ReductionT {
   using ReductionIdentifiers = ListT<type::ReductionIdentifierT<I, E>>;
   ENUM(ReductionModifier, Default, Inscan, Task);
   using TupleTrait = std::true_type;
-  std::tuple<ReductionIdentifiers, OPT(ReductionModifier), List> t;
+  std::tuple<OPT(ReductionModifier), ReductionIdentifiers, List> t;
 };
 
 // V5.2: [15.8.1] `memory-order` clauses