diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -11001,6 +11001,9 @@
   "'append_args' is not allowed with varargs functions">;
 def err_openmp_vla_in_task_untied : Error<
   "variable length arrays are not supported in OpenMP tasking regions with 'untied' clause">;
+def warn_omp_unterminated_declare_target : Warning<
+  "expected '#pragma omp end declare target' at end of file to match '#pragma omp %0'">,
+  InGroup<SourceUsesOpenMP>;
 } // end of OpenMP category
 
 let CategoryName = "Related Result Type Issue" in {
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -10769,6 +10769,10 @@
   /// encountered.
   void ActOnFinishedOpenMPDeclareTargetContext(DeclareTargetContextInfo &DTCI);
 
+  /// Report unterminated 'omp declare target' or 'omp begin declare target' at
+  /// the end of a compilation unit.
+  void DiagnoseUnterminatedOpenMPDeclareTarget();
+
   /// Searches for the provided declaration name for OpenMP declare target
   /// directive.
   NamedDecl *lookupOpenMPDeclareTargetName(Scope *CurScope,
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -1157,6 +1157,7 @@
 
   DiagnoseUnterminatedPragmaAlignPack();
   DiagnoseUnterminatedPragmaAttribute();
+  DiagnoseUnterminatedOpenMPDeclareTarget();
 
   // All delayed member exception specs should be checked or we end up accepting
   // incompatible declarations.
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -22101,6 +22101,14 @@
     ActOnOpenMPDeclareTargetName(It.first, It.second.Loc, It.second.MT, DTCI);
 }
 
+void Sema::DiagnoseUnterminatedOpenMPDeclareTarget() {
+  if (DeclareTargetNesting.empty())
+    return;
+  DeclareTargetContextInfo &DTCI = DeclareTargetNesting.back();
+  Diag(DTCI.Loc, diag::warn_omp_unterminated_declare_target)
+      << getOpenMPDirectiveName(DTCI.Kind);
+}
+
 NamedDecl *Sema::lookupOpenMPDeclareTargetName(Scope *CurScope,
                                                CXXScopeSpec &ScopeSpec,
                                                const DeclarationNameInfo &Id) {
diff --git a/clang/test/OpenMP/Inputs/unterminated_declare_target_include.h b/clang/test/OpenMP/Inputs/unterminated_declare_target_include.h
new file mode 100644
--- /dev/null
+++ b/clang/test/OpenMP/Inputs/unterminated_declare_target_include.h
@@ -0,0 +1,3 @@
+// expected-warning@+1 {{expected '#pragma omp end declare target' at end of file to match '#pragma omp declare target'}}
+#pragma omp declare target
+void zxy();
diff --git a/clang/test/OpenMP/declare_target_messages.cpp b/clang/test/OpenMP/declare_target_messages.cpp
--- a/clang/test/OpenMP/declare_target_messages.cpp
+++ b/clang/test/OpenMP/declare_target_messages.cpp
@@ -6,6 +6,9 @@
 // RUN: %clang_cc1 -triple x86_64-apple-macos10.7.0 -verify=expected,omp5,host5 -fopenmp-simd -fopenmp-is-device -fopenmp-targets=x86_64-apple-macos10.7.0 -fnoopenmp-use-tls -ferror-limit 100 -o - %s
 // RUN: %clang_cc1 -triple x86_64-apple-macos10.7.0 -verify=expected,omp45 -fopenmp-version=45 -fopenmp-simd -fnoopenmp-use-tls -ferror-limit 100 -o - %s
 // RUN: %clang_cc1 -triple x86_64-apple-macos10.7.0 -verify=expected,omp51 -fopenmp -fopenmp-version=51 -fnoopenmp-use-tls -ferror-limit 100 -o - %s
+// RUN: %clang_cc1 -triple x86_64-apple-macos10.7.0 -verify=expected,omp51 -fopenmp -fopenmp-version=51 -fnoopenmp-use-tls -ferror-limit 100 -DTESTEND=1 -o - %s
+// RUN: %clang_cc1 -triple x86_64-apple-macos10.7.0 -verify=expected,omp51 -fopenmp -fopenmp-version=51 -fnoopenmp-use-tls -ferror-limit 100 -I%S/Inputs -DTESTENDINC=1 -o - %s
+// RUN: %clang_cc1 -triple x86_64-apple-macos10.7.0 -verify=expected,omp51 -fopenmp-version=51 -fopenmp-simd -fnoopenmp-use-tls -ferror-limit 100 -o - %s
 // RUN: %clang_cc1 -triple x86_64-apple-macos10.7.0 -verify=expected,omp51 -fopenmp-version=51 -fopenmp-simd -fnoopenmp-use-tls -ferror-limit 100 -o - %s
 
 // RUN: %clang_cc1 -triple x86_64-apple-macos10.7.0 -verify=expected,omp5 -fopenmp -fnoopenmp-use-tls -ferror-limit 100 -o - %s
@@ -228,5 +231,12 @@
 #pragma omp declare target to(MultiDevTy) device_type(host)   // omp45-error {{unexpected 'device_type' clause, only 'to' or 'link' clauses expected}} omp5-error {{'device_type(host)' does not match previously specified 'device_type(any)' for the same declaration}} omp51-error {{'device_type(host)' does not match previously specified 'device_type(any)' for the same declaration}}
 #pragma omp declare target to(MultiDevTy) device_type(nohost) // omp45-error {{unexpected 'device_type' clause, only 'to' or 'link' clauses expected}} omp5-error {{'device_type(nohost)' does not match previously specified 'device_type(any)' for the same declaration}} // omp51-error {{'device_type(nohost)' does not match previously specified 'device_type(any)' for the same declaration}}
 
-// TODO: Issue an error message error {{expected '#pragma omp end declare target'}} note {{to match this '#pragma omp declare target'}}
+#if TESTENDINC
+#include "unterminated_declare_target_include.h"
+#elif TESTEND
+// expected-warning@+1 {{expected '#pragma omp end declare target' at end of file to match '#pragma omp declare target'}}
 #pragma omp declare target
+#else
+// expected-warning@+1 {{expected '#pragma omp end declare target' at end of file to match '#pragma omp begin declare target'}}
+#pragma omp begin declare target
+#endif