Index: flang/lib/Semantics/check-omp-structure.h
===================================================================
--- flang/lib/Semantics/check-omp-structure.h
+++ flang/lib/Semantics/check-omp-structure.h
@@ -225,6 +225,8 @@
   void CheckCycleConstraints(const parser::OpenMPLoopConstruct &x);
   void CheckDistLinear(const parser::OpenMPLoopConstruct &x);
   void CheckSIMDNest(const parser::OpenMPConstruct &x);
+  void CheckCancellationNest(
+      const parser::CharBlock &source, const parser::OmpCancelType::Type &type);
   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
@@ -846,7 +846,9 @@
 
 void OmpStructureChecker::Enter(const parser::OpenMPCancelConstruct &x) {
   const auto &dir{std::get<parser::Verbatim>(x.t)};
+  const auto &type{std::get<parser::OmpCancelType>(x.t)};
   PushContextAndClauseSets(dir.source, llvm::omp::Directive::OMPD_cancel);
+  CheckCancellationNest(dir.source, type.v);
 }
 
 void OmpStructureChecker::Leave(const parser::OpenMPCancelConstruct &) {
@@ -867,8 +869,10 @@
 void OmpStructureChecker::Enter(
     const parser::OpenMPCancellationPointConstruct &x) {
   const auto &dir{std::get<parser::Verbatim>(x.t)};
+  const auto &type{std::get<parser::OmpCancelType>(x.t)};
   PushContextAndClauseSets(
       dir.source, llvm::omp::Directive::OMPD_cancellation_point);
+  CheckCancellationNest(dir.source, type.v);
 }
 
 void OmpStructureChecker::Leave(
@@ -876,6 +880,62 @@
   dirContext_.pop_back();
 }
 
+void OmpStructureChecker::CheckCancellationNest(
+    const parser::CharBlock &source, const parser::OmpCancelType::Type &type) {
+  if (CurrentDirectiveIsNested()) {
+    OmpDirectiveSet allowedTaskgroupSet{
+        llvm::omp::Directive::OMPD_task, llvm::omp::Directive::OMPD_taskloop};
+    OmpDirectiveSet allowedSectionsSet{llvm::omp::Directive::OMPD_sections,
+        llvm::omp::Directive::OMPD_parallel_sections};
+    OmpDirectiveSet allowedDoSet{llvm::omp::Directive::OMPD_do,
+        llvm::omp::Directive::OMPD_distribute_parallel_do,
+        llvm::omp::Directive::OMPD_parallel_do,
+        llvm::omp::Directive::OMPD_target_parallel_do,
+        llvm::omp::Directive::OMPD_target_teams_distribute_parallel_do,
+        llvm::omp::Directive::OMPD_teams_distribute_parallel_do};
+    OmpDirectiveSet allowedParallelSet{llvm::omp::Directive::OMPD_parallel,
+        llvm::omp::Directive::OMPD_target_parallel};
+
+    bool eligibleCancellation{false};
+    switch (type) {
+    case parser::OmpCancelType::Type::Taskgroup:
+      if (allowedTaskgroupSet.test(GetContextParent().directive)) {
+        eligibleCancellation = true;
+      }
+      break;
+    case parser::OmpCancelType::Type::Sections:
+      if (allowedSectionsSet.test(GetContextParent().directive)) {
+        eligibleCancellation = true;
+      }
+      break;
+    case Fortran::parser::OmpCancelType::Type::Do:
+      if (allowedDoSet.test(GetContextParent().directive)) {
+        eligibleCancellation = true;
+      }
+      break;
+    case parser::OmpCancelType::Type::Parallel:
+      if (allowedParallelSet.test(GetContextParent().directive)) {
+        eligibleCancellation = true;
+      }
+      break;
+    default:
+      break;
+    }
+    if (!eligibleCancellation) {
+      context_.Say(source,
+          "%s %s construct cannot be closely nested inside %s "
+          "construct"_err_en_US,
+          ContextDirectiveAsFortran(),
+          parser::ToUpperCaseLetters(parser::OmpCancelType::EnumToString(type)),
+          parser::ToUpperCaseLetters(
+              getDirectiveName(GetContextParent().directive).str()));
+    }
+  } else {
+    context_.Say(source, "orphaned %s directives are prohibited"_err_en_US,
+        ContextDirectiveAsFortran());
+  }
+}
+
 void OmpStructureChecker::Enter(const parser::OmpEndBlockDirective &x) {
   const auto &dir{std::get<parser::OmpBlockDirective>(x.t)};
   ResetPartialContext(dir.source);
Index: flang/test/Semantics/omp-clause-validity01.f90
===================================================================
--- flang/test/Semantics/omp-clause-validity01.f90
+++ flang/test/Semantics/omp-clause-validity01.f90
@@ -494,9 +494,6 @@
   !ERROR: RELAXED clause is not allowed on the FLUSH directive
   !$omp flush relaxed
 
-  !$omp cancel DO
-  !$omp cancellation point parallel
-
 ! 2.13.2 critical Construct
 
   ! !$omp critical (first)
Index: flang/test/Semantics/omp-nested-cancel.f90
===================================================================
--- /dev/null
+++ flang/test/Semantics/omp-nested-cancel.f90
@@ -0,0 +1,161 @@
+! RUN: %S/test_errors.sh %s %t %flang -fopenmp
+! REQUIRES: shell
+
+! OpenMP Version 5.0
+! Check OpenMP construct validity for the following directives:
+! 2.18.1 Cancel Construct
+
+program main
+  integer :: i, N = 10
+  real :: a
+
+  !ERROR: orphaned CANCEL directives are prohibited
+  !$omp cancel taskgroup
+
+  !ERROR: orphaned CANCEL directives are prohibited
+  !$omp cancel sections
+
+  !ERROR: orphaned CANCEL directives are prohibited
+  !$omp cancel do
+
+  !ERROR: orphaned CANCEL directives are prohibited
+  !$omp cancel parallel
+
+  !$omp task
+  !$omp cancel taskgroup
+  a = 3.14
+  !$omp end task
+
+  !$omp taskloop
+  do i = 1, N
+    !$omp parallel
+    !$omp end parallel
+    !$omp cancel taskgroup
+    a = 3.14
+  end do
+  !$omp end taskloop
+
+  !$omp taskloop nogroup
+  do i = 1, N
+    !$omp cancel taskgroup
+    a = 3.14
+  end do
+
+  !$omp parallel
+  !ERROR: CANCEL TASKGROUP construct cannot be closely nested inside PARALLEL construct
+  !$omp cancel taskgroup
+  a = 3.14
+  !$omp end parallel
+
+  !$omp parallel
+  !$omp sections
+  !$omp cancel sections
+  !$omp section
+  a = 3.14
+  !$omp end sections
+  !$omp end parallel
+
+  !$omp sections
+  !$omp section
+  !$omp cancel sections
+  a = 3.14
+  !$omp end sections
+
+  !$omp parallel
+  !ERROR: CANCEL SECTIONS construct cannot be closely nested inside PARALLEL construct
+  !$omp cancel sections
+  a = 3.14
+  !$omp end parallel
+
+  !$omp parallel sections
+  !$omp cancel sections
+  a = 3.14
+  !$omp end parallel sections
+
+  !$omp do
+  do i = 1, N
+    a = 3.14
+    !$omp cancel do
+  end do
+  !$omp end do
+
+  !$omp parallel do
+  do i = 1, N
+    a = 3.14
+    !$omp cancel do
+  end do
+  !$omp end parallel do
+
+  !$omp target
+  !$omp teams
+  !$omp distribute parallel do
+  do i = 1, N
+    a = 3.14
+    !$omp cancel do
+  end do
+  !$omp end distribute parallel do
+  !$omp end teams
+  !$omp end target
+
+  !$omp target
+  !$omp teams distribute parallel do
+  do i = 1, N
+    a = 3.14
+    !$omp cancel do
+  end do
+  !$omp end teams distribute parallel do
+  !$omp end target
+
+  !$omp target teams distribute parallel do
+  do i = 1, N
+    a = 3.14
+    !$omp cancel do
+  end do
+  !$omp end target teams distribute parallel do
+
+  !$omp target parallel do
+  do i = 1, N
+    a = 3.14
+    !$omp cancel do
+  end do
+  !$omp end target parallel do
+
+  !$omp parallel
+  do i = 1, N
+    a = 3.14
+    !ERROR: CANCEL DO construct cannot be closely nested inside PARALLEL construct
+    !$omp cancel do
+  end do
+  !$omp end parallel
+
+  !$omp parallel
+  do i = 1, N
+    a = 3.14
+    !$omp cancel parallel
+  end do
+  !$omp end parallel
+
+  !$omp target parallel
+  do i = 1, N
+    a = 3.14
+    !$omp cancel parallel
+  end do
+  !$omp end target parallel
+
+  !$omp target parallel do
+  do i = 1, N
+    a = 3.14
+    !ERROR: CANCEL PARALLEL construct cannot be closely nested inside TARGET PARALLEL DO construct
+    !$omp cancel parallel
+  end do
+  !$omp end target parallel do
+
+  !$omp do
+  do i = 1, N
+    a = 3.14
+    !ERROR: CANCEL PARALLEL construct cannot be closely nested inside DO construct
+    !$omp cancel parallel
+  end do
+  !$omp end do
+
+end program main
Index: flang/test/Semantics/omp-nested-cancellation-point.f90
===================================================================
--- /dev/null
+++ flang/test/Semantics/omp-nested-cancellation-point.f90
@@ -0,0 +1,161 @@
+! RUN: %S/test_errors.sh %s %t %flang -fopenmp
+! REQUIRES: shell
+
+! OpenMP Version 5.0
+! Check OpenMP construct validity for the following directives:
+! 2.18.2 Cancellation Point Construct
+
+program main
+  integer :: i, N = 10
+  real :: a
+
+  !ERROR: orphaned CANCELLATION POINT directives are prohibited
+  !$omp cancellation point taskgroup
+
+  !ERROR: orphaned CANCELLATION POINT directives are prohibited
+  !$omp cancellation point sections
+
+  !ERROR: orphaned CANCELLATION POINT directives are prohibited
+  !$omp cancellation point do
+
+  !ERROR: orphaned CANCELLATION POINT directives are prohibited
+  !$omp cancellation point parallel
+
+  !$omp task
+  !$omp cancellation point taskgroup
+  a = 3.14
+  !$omp end task
+
+  !$omp taskloop
+  do i = 1, N
+    !$omp parallel
+    !$omp end parallel
+    !$omp cancellation point taskgroup
+    a = 3.14
+  end do
+  !$omp end taskloop
+
+  !$omp taskloop nogroup
+  do i = 1, N
+    !$omp cancellation point taskgroup
+    a = 3.14
+  end do
+
+  !$omp parallel
+  !ERROR: CANCELLATION POINT TASKGROUP construct cannot be closely nested inside PARALLEL construct
+  !$omp cancellation point taskgroup
+  a = 3.14
+  !$omp end parallel
+
+  !$omp parallel
+  !$omp sections
+  !$omp cancellation point sections
+  !$omp section
+  a = 3.14
+  !$omp end sections
+  !$omp end parallel
+
+  !$omp sections
+  !$omp section
+  !$omp cancellation point sections
+  a = 3.14
+  !$omp end sections
+
+  !$omp parallel
+  !ERROR: CANCELLATION POINT SECTIONS construct cannot be closely nested inside PARALLEL construct
+  !$omp cancellation point sections
+  a = 3.14
+  !$omp end parallel
+
+  !$omp parallel sections
+  !$omp cancellation point sections
+  a = 3.14
+  !$omp end parallel sections
+
+  !$omp do
+  do i = 1, N
+    a = 3.14
+    !$omp cancellation point do
+  end do
+  !$omp end do
+
+  !$omp parallel do
+  do i = 1, N
+    a = 3.14
+    !$omp cancellation point do
+  end do
+  !$omp end parallel do
+
+  !$omp target
+  !$omp teams
+  !$omp distribute parallel do
+  do i = 1, N
+    a = 3.14
+    !$omp cancellation point do
+  end do
+  !$omp end distribute parallel do
+  !$omp end teams
+  !$omp end target
+
+  !$omp target
+  !$omp teams distribute parallel do
+  do i = 1, N
+    a = 3.14
+    !$omp cancellation point do
+  end do
+  !$omp end teams distribute parallel do
+  !$omp end target
+
+  !$omp target teams distribute parallel do
+  do i = 1, N
+    a = 3.14
+    !$omp cancellation point do
+  end do
+  !$omp end target teams distribute parallel do
+
+  !$omp target parallel do
+  do i = 1, N
+    a = 3.14
+    !$omp cancellation point do
+  end do
+  !$omp end target parallel do
+
+  !$omp parallel
+  do i = 1, N
+    a = 3.14
+    !ERROR: CANCELLATION POINT DO construct cannot be closely nested inside PARALLEL construct
+    !$omp cancellation point do
+  end do
+  !$omp end parallel
+
+  !$omp parallel
+  do i = 1, N
+    a = 3.14
+    !$omp cancellation point parallel
+  end do
+  !$omp end parallel
+
+  !$omp target parallel
+  do i = 1, N
+    a = 3.14
+    !$omp cancellation point parallel
+  end do
+  !$omp end target parallel
+
+  !$omp target parallel do
+  do i = 1, N
+    a = 3.14
+    !ERROR: CANCELLATION POINT PARALLEL construct cannot be closely nested inside TARGET PARALLEL DO construct
+    !$omp cancellation point parallel
+  end do
+  !$omp end target parallel do
+
+  !$omp do
+  do i = 1, N
+    a = 3.14
+    !ERROR: CANCELLATION POINT PARALLEL construct cannot be closely nested inside DO construct
+    !$omp cancellation point parallel
+  end do
+  !$omp end do
+
+end program main