Index: flang/lib/Semantics/check-directive-structure.h
===================================================================
--- flang/lib/Semantics/check-directive-structure.h
+++ flang/lib/Semantics/check-directive-structure.h
@@ -203,12 +203,6 @@
     GetContext().actualClauses.push_back(type);
   }
 
-  void EnterSIMDNest() { simdNest_++; }
-
-  void ExitSIMDNest() { simdNest_--; }
-
-  int GetSIMDNest() { return simdNest_; }
-
   // Check if the given clause is present in the current context
   const PC *FindClause(C type) {
     auto it{GetContext().clauseInfo.find(type)};
@@ -320,7 +314,6 @@
       directiveClausesMap_;
 
   std::string ClauseSetToString(const common::EnumSet<C, ClauseEnumSize> set);
-  int simdNest_{0};
 };
 
 template <typename D, typename C, typename PC, std::size_t ClauseEnumSize>
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 &);
@@ -246,6 +247,12 @@
   void CheckPredefinedAllocatorRestriction(
       const parser::CharBlock &source, const parser::Name &name);
   bool isPredefinedAllocator{false};
+  void EnterDirectiveNest(const int index) { directiveNest_[index]++; }
+  void ExitDirectiveNest(const int index) { directiveNest_[index]--; }
+  int GetDirectiveNest(const int index) { return directiveNest_[index]; }
+
+  enum directiveNestType { SIMDNest, TargetNest, LastType };
+  int directiveNest_[LastType + 1] = {0};
 };
 } // namespace Fortran::semantics
 #endif // FORTRAN_SEMANTICS_CHECK_OMP_STRUCTURE_H_
Index: flang/lib/Semantics/check-omp-structure.cpp
===================================================================
--- flang/lib/Semantics/check-omp-structure.cpp
+++ flang/lib/Semantics/check-omp-structure.cpp
@@ -285,9 +285,12 @@
   // called individually for each construct.  Therefore a
   // dirContext_ size `1` means the current construct is nested
   if (dirContext_.size() >= 1) {
-    if (GetSIMDNest() > 0) {
+    if (GetDirectiveNest(SIMDNest) > 0) {
       CheckSIMDNest(x);
     }
+    if (GetDirectiveNest(TargetNest) > 0) {
+      CheckTargetNest(x);
+    }
   }
 }
 
@@ -306,7 +309,7 @@
 
   PushContextAndClauseSets(beginDir.source, beginDir.v);
   if (llvm::omp::simdSet.test(GetContext().directive)) {
-    EnterSIMDNest();
+    EnterDirectiveNest(SIMDNest);
   }
 
   if (beginDir.v == llvm::omp::Directive::OMPD_do) {
@@ -473,6 +476,53 @@
   }
 }
 
+void OmpStructureChecker::CheckTargetNest(const parser::OpenMPConstruct &c) {
+  // 2.12.5 Target Construct Restriction
+  bool eligibleTarget{true};
+  llvm::omp::Directive ineligibleTargetDir;
+  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 = false;
+              ineligibleTargetDir = 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 = false;
+                        ineligibleTargetDir = dir.v;
+                      }
+                    },
+                    [&](const auto &c) {},
+                },
+                c.u);
+          },
+          [&](const auto &c) {},
+      },
+      c.u);
+  if (!eligibleTarget) {
+    context_.Say(parser::FindSourceLocation(c),
+        "If %s directive is nested inside TARGET region, the behaviour "
+        "is unspecified"_en_US,
+        parser::ToUpperCaseLetters(
+            getDirectiveName(ineligibleTargetDir).str()));
+  }
+}
+
 std::int64_t OmpStructureChecker::GetOrdCollapseLevel(
     const parser::OpenMPLoopConstruct &x) {
   const auto &beginLoopDir{std::get<parser::OmpBeginLoopDirective>(x.t)};
@@ -585,7 +635,7 @@
 
 void OmpStructureChecker::Leave(const parser::OpenMPLoopConstruct &) {
   if (llvm::omp::simdSet.test(GetContext().directive)) {
-    ExitSIMDNest();
+    ExitDirectiveNest(SIMDNest);
   }
   dirContext_.pop_back();
 }
@@ -616,6 +666,9 @@
   CheckMatching<parser::OmpBlockDirective>(beginDir, endDir);
 
   PushContextAndClauseSets(beginDir.source, beginDir.v);
+  if (GetContext().directive == llvm::omp::Directive::OMPD_target) {
+    EnterDirectiveNest(TargetNest);
+  }
 
   if (CurrentDirectiveIsNested()) {
     CheckIfDoOrderedClause(beginDir);
@@ -683,6 +736,9 @@
 }
 
 void OmpStructureChecker::Leave(const parser::OpenMPBlockConstruct &) {
+  if (GetContext().directive == llvm::omp::Directive::OMPD_target) {
+    ExitDirectiveNest(TargetNest);
+  }
   dirContext_.pop_back();
 }
 
Index: flang/test/Semantics/omp-nested-target.f90
===================================================================
--- /dev/null
+++ flang/test/Semantics/omp-nested-target.f90
@@ -0,0 +1,54 @@
+! RUN: %S/test_errors.sh %s %t %flang_fc1 -fopenmp
+! REQUIRES: shell
+
+! OpenMP Version 5.0
+! Check OpenMP construct 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(:)
+
+  !$omp target
+  !WARNING: If TARGET UPDATE directive is nested inside TARGET region, the behaviour is unspecified
+  !$omp target update from(arrayA) to(arrayB)
+  do i = 1, 512
+    arrayA(i) = arrayB(i)
+  end do
+  !$omp end target
+
+  !$omp parallel
+  !$omp target
+  !$omp parallel
+  !WARNING: If TARGET UPDATE directive is nested inside TARGET region, the behaviour is unspecified
+  !$omp target update from(arrayA) to(arrayB)
+  do i = 1, 512
+    arrayA(i) = arrayB(i)
+  end do
+  !$omp end parallel
+  !$omp end target
+  !$omp end parallel
+
+  !$omp target
+  !WARNING: If TARGET DATA directive is nested inside TARGET region, the behaviour is unspecified
+  !$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))
+  !$omp target
+  !WARNING: If TARGET ENTER DATA directive is nested inside TARGET region, the behaviour is unspecified
+  !$omp target enter data map(alloc:B)
+  !$omp end target
+
+  !$omp target
+  !WARNING: If TARGET EXIT DATA directive is nested inside TARGET region, the behaviour is unspecified
+  !$omp target exit data map(delete:B)
+  !$omp end target
+  deallocate(B)
+
+end program main