diff --git a/flang/include/flang/Parser/dump-parse-tree.h b/flang/include/flang/Parser/dump-parse-tree.h
--- a/flang/include/flang/Parser/dump-parse-tree.h
+++ b/flang/include/flang/Parser/dump-parse-tree.h
@@ -82,6 +82,7 @@
   NODE(parser, AccObjectListWithModifier)
   NODE(parser, AccObjectListWithReduction)
   NODE(parser, AccReductionOperator)
+  NODE_ENUM(parser::AccReductionOperator, Operator)
   NODE(parser, AccSizeExpr)
   NODE(parser, AccSizeExprList)
   NODE(parser, AccStandaloneDirective)
diff --git a/flang/include/flang/Parser/parse-tree.h b/flang/include/flang/Parser/parse-tree.h
--- a/flang/include/flang/Parser/parse-tree.h
+++ b/flang/include/flang/Parser/parse-tree.h
@@ -3840,8 +3840,10 @@
 
 // 2.5.13: + | * | max | min | iand | ior | ieor | .and. | .or. | .eqv. | .neqv.
 struct AccReductionOperator {
-  UNION_CLASS_BOILERPLATE(AccReductionOperator);
-  std::variant<DefinedOperator, ProcedureDesignator> u;
+  ENUM_CLASS(
+      Operator, Plus, Multiply, Max, Min, Iand, Ior, Ieor, And, Or, Eqv, Neqv)
+  WRAPPER_CLASS_BOILERPLATE(AccReductionOperator, Operator);
+  CharBlock source;
 };
 
 struct AccObjectListWithReduction {
diff --git a/flang/lib/Parser/openacc-parsers.cpp b/flang/lib/Parser/openacc-parsers.cpp
--- a/flang/lib/Parser/openacc-parsers.cpp
+++ b/flang/lib/Parser/openacc-parsers.cpp
@@ -145,8 +145,19 @@
         maybe(","_tok / "STATIC:" >> Parser<AccSizeExpr>{})))
 
 // 2.5.13 Reduction
-TYPE_PARSER(construct<AccReductionOperator>(Parser<DefinedOperator>{}) ||
-    construct<AccReductionOperator>(Parser<ProcedureDesignator>{}))
+// Operator for reduction
+TYPE_PARSER(sourced(construct<AccReductionOperator>(
+    first("+" >> pure(AccReductionOperator::Operator::Plus),
+        "*" >> pure(AccReductionOperator::Operator::Multiply),
+        "MAX" >> pure(AccReductionOperator::Operator::Max),
+        "MIN" >> pure(AccReductionOperator::Operator::Min),
+        "IAND" >> pure(AccReductionOperator::Operator::Iand),
+        "IOR" >> pure(AccReductionOperator::Operator::Ior),
+        "IEOR" >> pure(AccReductionOperator::Operator::Ieor),
+        ".AND." >> pure(AccReductionOperator::Operator::And),
+        ".OR." >> pure(AccReductionOperator::Operator::Or),
+        ".EQV." >> pure(AccReductionOperator::Operator::Eqv),
+        ".NEQV." >> pure(AccReductionOperator::Operator::Neqv)))))
 
 // 2.5.14 Default clause
 TYPE_PARSER(construct<AccDefaultClause>(
diff --git a/flang/lib/Parser/unparse.cpp b/flang/lib/Parser/unparse.cpp
--- a/flang/lib/Parser/unparse.cpp
+++ b/flang/lib/Parser/unparse.cpp
@@ -1923,6 +1923,9 @@
         x.u);
   }
   void Unparse(const AccObjectList &x) { Walk(x.v, ","); }
+  void Unparse(const AccReductionOperator::Operator &x) {
+    Word(AccReductionOperator::EnumToString(x));
+  }
   void Unparse(const AccObjectListWithReduction &x) {
     Walk(std::get<AccReductionOperator>(x.t));
     Put(":");
diff --git a/flang/test/Semantics/acc-clause-validity.f90 b/flang/test/Semantics/acc-clause-validity.f90
--- a/flang/test/Semantics/acc-clause-validity.f90
+++ b/flang/test/Semantics/acc-clause-validity.f90
@@ -18,8 +18,13 @@
 
   implicit none
 
-  integer :: i, j
-  integer :: N = 256
+  integer :: i, j, b
+  integer, parameter :: N = 256
+  integer, dimension(N) :: c
+  logical, dimension(N) :: d, e
+  real :: reduction_r
+  logical :: reduction_l
+
   !ERROR: At least one clause is required on the DECLARE directive
   !$acc declare
   real(8) :: a(256)
@@ -187,6 +192,61 @@
   !ERROR: Unmatched END PARALLEL LOOP directive
   !$acc end parallel loop
 
+  !$acc parallel loop reduction(+: reduction_r)
+  do i = 1, N
+    reduction_r = a(i) + i
+  end do
+
+  !$acc parallel loop reduction(*: reduction_r)
+  do i = 1, N
+    reduction_r = reduction_r * (a(i) + i)
+  end do
+
+  !$acc parallel loop reduction(min: reduction_r)
+  do i = 1, N
+    reduction_r = min(reduction_r, a(i) * i)
+  end do
+
+  !$acc parallel loop reduction(max: reduction_r)
+  do i = 1, N
+    reduction_r = max(reduction_r, a(i) * i)
+  end do
+
+  !$acc parallel loop reduction(iand: b)
+  do i = 1, N
+    b = iand(b, c(i))
+  end do
+
+  !$acc parallel loop reduction(ior: b)
+  do i = 1, N
+    b = ior(b, c(i))
+  end do
+
+  !$acc parallel loop reduction(ieor: b)
+  do i = 1, N
+    b = ieor(b, c(i))
+  end do
+
+  !$acc parallel loop reduction(.and.: reduction_l)
+  do i = 1, N
+    reduction_l = d(i) .and. e(i)
+  end do
+
+  !$acc parallel loop reduction(.or.: reduction_l)
+  do i = 1, N
+    reduction_l = d(i) .or. e(i)
+  end do
+
+  !$acc parallel loop reduction(.eqv.: reduction_l)
+  do i = 1, N
+    reduction_l = d(i) .eqv. e(i)
+  end do
+
+  !$acc parallel loop reduction(.neqv.: reduction_l)
+  do i = 1, N
+    reduction_l = d(i) .neqv. e(i)
+  end do
+
   !$acc kernels wait(1, 2) async(3)
   !$acc end kernels