Index: flang/lib/Semantics/check-omp-structure.h
===================================================================
--- flang/lib/Semantics/check-omp-structure.h
+++ flang/lib/Semantics/check-omp-structure.h
@@ -225,6 +225,7 @@
   void CheckCycleConstraints(const parser::OpenMPLoopConstruct &x);
   void CheckDistLinear(const parser::OpenMPLoopConstruct &x);
   void CheckSIMDNest(const parser::OpenMPConstruct &x);
+  void CheckTARGETNest(const parser::OpenMPConstruct &x);
   std::int64_t GetOrdCollapseLevel(const parser::OpenMPLoopConstruct &x);
   void CheckIfDoOrderedClause(const parser::OmpBlockDirective &blkDirectiv);
   bool CheckReductionOperators(const parser::OmpClause::Reduction &);
Index: flang/lib/Semantics/check-omp-structure.cpp
===================================================================
--- flang/lib/Semantics/check-omp-structure.cpp
+++ flang/lib/Semantics/check-omp-structure.cpp
@@ -288,6 +288,9 @@
     if (GetSIMDNest() > 0) {
       CheckSIMDNest(x);
     }
+    if (GetContext().directive == llvm::omp::Directive::OMPD_target) {
+      CheckTARGETNest(x);
+    }
   }
 }
 
@@ -473,6 +476,51 @@
   }
 }
 
+void OmpStructureChecker::CheckTARGETNest(const parser::OpenMPConstruct &c) {
+  // 2.12.5 Target Construct Restriction
+  bool eligibleTARGET{false};
+  llvm::omp::Directive directive;
+  std::visit(
+      common::visitors{
+          [&](const parser::OpenMPBlockConstruct &c) {
+            const auto &beginBlockDir{
+                std::get<parser::OmpBeginBlockDirective>(c.t)};
+            const auto &beginDir{
+                std::get<parser::OmpBlockDirective>(beginBlockDir.t)};
+            if (beginDir.v == llvm::omp::Directive::OMPD_target_data) {
+              eligibleTARGET = true;
+              directive = beginDir.v;
+            }
+          },
+          [&](const parser::OpenMPStandaloneConstruct &c) {
+            std::visit(
+                common::visitors{
+                    [&](const parser::OpenMPSimpleStandaloneConstruct &c) {
+                      const auto &dir{
+                          std::get<parser::OmpSimpleStandaloneDirective>(c.t)};
+                      if (dir.v == llvm::omp::Directive::OMPD_target_update ||
+                          dir.v ==
+                              llvm::omp::Directive::OMPD_target_enter_data ||
+                          dir.v ==
+                              llvm::omp::Directive::OMPD_target_exit_data) {
+                        eligibleTARGET = true;
+                        directive = dir.v;
+                      }
+                    },
+                    [&](const auto &c) {},
+                },
+                c.u);
+          },
+          [&](const auto &c) {},
+      },
+      c.u);
+  if (eligibleTARGET) {
+    context_.Say(parser::FindSourceLocation(c),
+        "%s directive cannot be nested inside TARGET region"_err_en_US,
+        parser::ToUpperCaseLetters(getDirectiveName(directive).str()));
+  }
+}
+
 std::int64_t OmpStructureChecker::GetOrdCollapseLevel(
     const parser::OpenMPLoopConstruct &x) {
   const auto &beginLoopDir{std::get<parser::OmpBeginLoopDirective>(x.t)};
Index: flang/test/Semantics/omp-target01.f90
===================================================================
--- /dev/null
+++ flang/test/Semantics/omp-target01.f90
@@ -0,0 +1,42 @@
+! RUN: %S/test_errors.sh %s %t %flang -fopenmp
+! REQUIRES: shell
+
+! OpenMP Version 5.0
+! Check OpenMP clause validity for the following directives:
+! 2.12.5 Target Construct
+
+program main
+  integer :: i, j, N = 10
+  real :: a, arrayA(512), arrayB(512), ai(10)
+  real, allocatable :: B(:)
+
+  !$omp target
+  !ERROR: TARGET UPDATE directive cannot be nested inside TARGET region
+  !$omp target update from(arrayA) to(arrayB)
+  do i = 1, 512
+    arrayA(i) = arrayB(i)
+  end do
+  !$omp end target
+
+  !$omp target
+  !ERROR: TARGET DATA directive cannot be nested inside TARGET region
+  !$omp target data map(to: a)
+  do i = 1, N
+    a = 3.14
+  end do
+  !$omp end target data
+  !$omp end target
+
+  allocate(B(N))
+  !$omp target
+  !ERROR: TARGET ENTER DATA directive cannot be nested inside TARGET region
+  !$omp target enter data map(alloc:B)
+  !$omp end target
+
+  !$omp target
+  !ERROR: TARGET EXIT DATA directive cannot be nested inside TARGET region
+  !$omp target exit data map(delete:B)
+  !$omp end target
+  deallocate(B)
+
+end program main