diff --git a/flang/examples/FeatureList/FeatureList.cpp b/flang/examples/FeatureList/FeatureList.cpp
--- a/flang/examples/FeatureList/FeatureList.cpp
+++ b/flang/examples/FeatureList/FeatureList.cpp
@@ -80,7 +80,7 @@
   READ_FEATURE(AccEndAtomic)
   READ_FEATURE(AccEndBlockDirective)
   READ_FEATURE(AccEndCombinedDirective)
-  READ_FEATURE(AccGangArgument)
+  READ_FEATURE(AccGangArg)
   READ_FEATURE(AccObject)
   READ_FEATURE(AccObjectList)
   READ_FEATURE(AccObjectListWithModifier)
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
@@ -81,7 +81,11 @@
   NODE(parser, AccEndAtomic)
   NODE(parser, AccEndBlockDirective)
   NODE(parser, AccEndCombinedDirective)
-  NODE(parser, AccGangArgument)
+  NODE(parser, AccGangArg)
+  NODE(AccGangArg, Num)
+  NODE(AccGangArg, Dim)
+  NODE(AccGangArg, Static)
+  NODE(parser, AccGangArgList)
   NODE(parser, AccObject)
   NODE(parser, AccObjectList)
   NODE(parser, AccObjectListWithModifier)
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
@@ -4020,9 +4020,7 @@
 };
 
 struct AccSizeExpr {
-  TUPLE_CLASS_BOILERPLATE(AccSizeExpr);
-  CharBlock source;
-  std::tuple<std::optional<ScalarIntExpr>> t; // if null then *
+  WRAPPER_CLASS_BOILERPLATE(AccSizeExpr, std::optional<ScalarIntExpr>);
 };
 
 struct AccSizeExprList {
@@ -4035,9 +4033,18 @@
   CharBlock source;
 };
 
-struct AccGangArgument {
-  TUPLE_CLASS_BOILERPLATE(AccGangArgument);
-  std::tuple<std::optional<ScalarIntExpr>, std::optional<AccSizeExpr>> t;
+// num, dim, static
+struct AccGangArg {
+  UNION_CLASS_BOILERPLATE(AccGangArg);
+  WRAPPER_CLASS(Num, ScalarIntExpr);
+  WRAPPER_CLASS(Dim, ScalarIntExpr);
+  WRAPPER_CLASS(Static, AccSizeExpr);
+  std::variant<Num, Dim, Static> u;
+  CharBlock source;
+};
+
+struct AccGangArgList {
+  WRAPPER_CLASS_BOILERPLATE(AccGangArgList, std::list<AccGangArg>);
 };
 
 struct AccClause {
diff --git a/flang/lib/Lower/OpenACC.cpp b/flang/lib/Lower/OpenACC.cpp
--- a/flang/lib/Lower/OpenACC.cpp
+++ b/flang/lib/Lower/OpenACC.cpp
@@ -648,25 +648,26 @@
     if (const auto *gangClause =
             std::get_if<Fortran::parser::AccClause::Gang>(&clause.u)) {
       if (gangClause->v) {
-        const Fortran::parser::AccGangArgument &x = *gangClause->v;
-        if (const auto &gangNumValue =
-                std::get<std::optional<Fortran::parser::ScalarIntExpr>>(x.t)) {
-          gangNum = fir::getBase(converter.genExprValue(
-              *Fortran::semantics::GetExpr(gangNumValue.value()), stmtCtx));
-        }
-        if (const auto &gangStaticValue =
-                std::get<std::optional<Fortran::parser::AccSizeExpr>>(x.t)) {
-          const auto &expr =
-              std::get<std::optional<Fortran::parser::ScalarIntExpr>>(
-                  gangStaticValue.value().t);
-          if (expr) {
-            gangStatic = fir::getBase(converter.genExprValue(
-                *Fortran::semantics::GetExpr(*expr), stmtCtx));
-          } else {
-            // * was passed as value and will be represented as a special
-            // constant.
-            gangStatic = firOpBuilder.createIntegerConstant(
-                clauseLocation, firOpBuilder.getIndexType(), starCst);
+        const Fortran::parser::AccGangArgList &x = *gangClause->v;
+        for (const Fortran::parser::AccGangArg &gangArg : x.v) {
+          if (const auto *num =
+                  std::get_if<Fortran::parser::AccGangArg::Num>(&gangArg.u)) {
+            gangNum = fir::getBase(converter.genExprValue(
+                *Fortran::semantics::GetExpr(num->v), stmtCtx));
+          } else if (const auto *staticArg =
+                         std::get_if<Fortran::parser::AccGangArg::Static>(
+                             &gangArg.u)) {
+
+            const Fortran::parser::AccSizeExpr &sizeExpr = staticArg->v;
+            if (sizeExpr.v) {
+              gangStatic = fir::getBase(converter.genExprValue(
+                  *Fortran::semantics::GetExpr(*sizeExpr.v), stmtCtx));
+            } else {
+              // * was passed as value and will be represented as a special
+              // constant.
+              gangStatic = firOpBuilder.createIntegerConstant(
+                  clauseLocation, firOpBuilder.getIndexType(), starCst);
+            }
           }
         }
       }
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
@@ -66,11 +66,20 @@
         "*" >> construct<std::optional<ScalarIntConstantExpr>>()))
 TYPE_PARSER(construct<AccTileExprList>(nonemptyList(Parser<AccTileExpr>{})))
 
-// 2.9 (1607) gang-arg is:
-//   [[num:]int-expr][[,]static:size-expr]
-TYPE_PARSER(construct<AccGangArgument>(
-    maybe(("NUM:"_tok >> scalarIntExpr || scalarIntExpr)),
-    maybe(", STATIC:" >> Parser<AccSizeExpr>{})))
+// 2.9 gang-arg is one of :
+//   [num:]int-expr
+//   dim:int-expr
+//   static:size-expr
+TYPE_PARSER(construct<AccGangArg>(construct<AccGangArg::Static>(
+                "STATIC: " >> Parser<AccSizeExpr>{})) ||
+    construct<AccGangArg>(
+        construct<AccGangArg::Dim>("DIM: " >> scalarIntExpr)) ||
+    construct<AccGangArg>(
+        construct<AccGangArg::Num>(maybe("NUM: "_tok) >> scalarIntExpr)))
+
+// 2.9 gang-arg-list
+TYPE_PARSER(
+    construct<AccGangArgList>(many(maybe(","_tok) >> Parser<AccGangArg>{})))
 
 // 2.5.13 Reduction
 // Operator for reduction
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
@@ -1884,9 +1884,19 @@
     }
   }
   void Unparse(const AccClauseList &x) { Walk(" ", x.v, " "); }
-  void Unparse(const AccGangArgument &x) {
-    Walk("NUM:", std::get<std::optional<ScalarIntExpr>>(x.t));
-    Walk(", STATIC:", std::get<std::optional<AccSizeExpr>>(x.t));
+  void Unparse(const AccGangArgList &x) { Walk(x.v, ","); }
+  void Before(const AccSizeExpr &x) {
+    if (!x.v)
+      Put("*");
+  }
+  void Before(const AccGangArg &x) {
+    common::visit(common::visitors{
+                      [&](const AccGangArg::Num &) { Word("NUM:"); },
+                      [&](const AccGangArg::Dim &) { Word("DIM:"); },
+                      [&](const AccGangArg::Static &) { Word("STATIC:"); },
+                      [](const StatOrErrmsg &) {},
+                  },
+        x.u);
   }
   void Unparse(const OpenACCBlockConstruct &x) {
     BeginOpenACC();
diff --git a/flang/lib/Semantics/check-acc-structure.cpp b/flang/lib/Semantics/check-acc-structure.cpp
--- a/flang/lib/Semantics/check-acc-structure.cpp
+++ b/flang/lib/Semantics/check-acc-structure.cpp
@@ -326,7 +326,6 @@
 CHECK_SIMPLE_CLAUSE(DeviceType, ACCC_device_type)
 CHECK_SIMPLE_CLAUSE(Finalize, ACCC_finalize)
 CHECK_SIMPLE_CLAUSE(Firstprivate, ACCC_firstprivate)
-CHECK_SIMPLE_CLAUSE(Gang, ACCC_gang)
 CHECK_SIMPLE_CLAUSE(Host, ACCC_host)
 CHECK_SIMPLE_CLAUSE(If, ACCC_if)
 CHECK_SIMPLE_CLAUSE(IfPresent, ACCC_if_present)
@@ -407,6 +406,26 @@
   }
 }
 
+void AccStructureChecker::Enter(const parser::AccClause::Gang &g) {
+  CheckAllowed(llvm::acc::Clause::ACCC_gang);
+
+  if (g.v) {
+    bool hasNum = false;
+    bool hasDim = false;
+    const Fortran::parser::AccGangArgList &x = *g.v;
+    for (const Fortran::parser::AccGangArg &gangArg : x.v) {
+      if (std::get_if<Fortran::parser::AccGangArg::Num>(&gangArg.u))
+        hasNum = true;
+      else if (std::get_if<Fortran::parser::AccGangArg::Dim>(&gangArg.u))
+        hasDim = true;
+    }
+
+    if (hasDim && hasNum)
+      context_.Say(GetContext().clauseSource,
+          "The num argument is not allowed when dim is specified"_err_en_US);
+  }
+}
+
 void AccStructureChecker::Enter(const parser::AccClause::Self &x) {
   CheckAllowed(llvm::acc::Clause::ACCC_self);
   const std::optional<parser::AccSelfClause> &accSelfClause = x.v;
diff --git a/flang/test/Parser/acc-unparse.f90 b/flang/test/Parser/acc-unparse.f90
--- a/flang/test/Parser/acc-unparse.f90
+++ b/flang/test/Parser/acc-unparse.f90
@@ -17,3 +17,53 @@
 
 !CHECK-LABEL: PROGRAM bug47659
 !CHECK: !$ACC PARALLEL LOOP
+
+subroutine acc_loop(a)
+  real :: a(10)
+  integer :: i, gangNum, gangDim, gangStatic
+
+! CHECK-LABEL: acc_loop
+
+  !$acc loop gang
+  do i = 1, 10
+    a(i) = i
+  end do
+! CHECK: !$ACC LOOP GANG
+
+  !$acc loop gang(gangNum)
+  do i = 1, 10
+    a(i) = i
+  end do
+! CHECK: !$ACC LOOP GANG(NUM:gangnum)
+
+  !$acc loop gang(num: gangNum)
+  do i = 1, 10
+    a(i) = i
+  end do
+! CHECK: !$ACC LOOP GANG(NUM:gangnum)
+
+  !$acc loop gang(dim: gangDim)
+  do i = 1, 10
+    a(i) = i
+  end do
+! CHECK: !$ACC LOOP GANG(DIM:gangdim)
+
+  !$acc loop gang(static:gangStatic)
+  do i = 1, 10
+    a(i) = i
+  end do
+! CHECK: !$ACC LOOP GANG(STATIC:gangstatic)
+
+  !$acc loop gang(static:*)
+  do i = 1, 10
+    a(i) = i
+  end do
+! CHECK: !$ACC LOOP GANG(STATIC:*)
+
+  !$acc loop gang(static:gangStatic, dim: gangDim)
+  do i = 1, 10
+    a(i) = i
+  end do
+! CHECK: !$ACC LOOP GANG(STATIC:gangstatic,DIM:gangdim)
+
+end subroutine
diff --git a/flang/test/Semantics/OpenACC/acc-loop.f90 b/flang/test/Semantics/OpenACC/acc-loop.f90
--- a/flang/test/Semantics/OpenACC/acc-loop.f90
+++ b/flang/test/Semantics/OpenACC/acc-loop.f90
@@ -257,4 +257,10 @@
       a(i) = 3.14
     end do
   end do
+
+  !ERROR: The num argument is not allowed when dim is specified
+  !$acc loop gang(1, dim: 2)
+  do i = 1, N
+  end do
+
 end program openacc_loop_validity
diff --git a/llvm/include/llvm/Frontend/OpenACC/ACC.td b/llvm/include/llvm/Frontend/OpenACC/ACC.td
--- a/llvm/include/llvm/Frontend/OpenACC/ACC.td
+++ b/llvm/include/llvm/Frontend/OpenACC/ACC.td
@@ -147,7 +147,7 @@
 
 // 2.9.2
 def ACCC_Gang : Clause<"gang"> {
-  let flangClass = "AccGangArgument";
+  let flangClass = "AccGangArgList";
   let isValueOptional = true;
 }