diff --git a/clang/include/clang/Driver/Driver.h b/clang/include/clang/Driver/Driver.h
index 774eac613a10..0781d476ec4a 100644
--- a/clang/include/clang/Driver/Driver.h
+++ b/clang/include/clang/Driver/Driver.h
@@ -44,9 +44,7 @@ typedef SmallVector<InputInfo, 4> InputInfoList;
 
 class Command;
 class Compilation;
-class JobList;
 class JobAction;
-class SanitizerArgs;
 class ToolChain;
 
 /// Describes the kind of LTO mode selected via -f(no-)?lto(=.*)? options.
diff --git a/clang/include/clang/Lex/PreprocessingRecord.h b/clang/include/clang/Lex/PreprocessingRecord.h
index 063929dd8f96..c97ca8628e14 100644
--- a/clang/include/clang/Lex/PreprocessingRecord.h
+++ b/clang/include/clang/Lex/PreprocessingRecord.h
@@ -49,7 +49,6 @@ void operator delete(void *ptr, clang::PreprocessingRecord &PR,
 
 namespace clang {
 
-class FileEntry;
 class IdentifierInfo;
 class MacroInfo;
 class SourceManager;
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
index 8fc24c731035..79454b5addea 100644
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -67,7 +67,6 @@ namespace clang {
 class CodeCompletionHandler;
 class CommentHandler;
 class DirectoryEntry;
-class DirectoryLookup;
 class EmptylineHandler;
 class ExternalPreprocessorSource;
 class FileEntry;
diff --git a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h
index 1092d1292255..9927b6340793 100644
--- a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h
+++ b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h
@@ -55,8 +55,6 @@ template <typename T> struct ProgramStateTrait {
   }
 };
 
-class RangeSet;
-
 /// \class ProgramState
 /// ProgramState - This class encapsulates:
 ///
diff --git a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SVals.h b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SVals.h
index c9c21fcf230e..2ae811ee3365 100644
--- a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SVals.h
+++ b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SVals.h
@@ -40,7 +40,6 @@ class LabelDecl;
 
 namespace ento {
 
-class BasicValueFactory;
 class CompoundValData;
 class LazyCompoundValData;
 class MemRegion;
diff --git a/clang/lib/CodeGen/SanitizerMetadata.h b/clang/lib/CodeGen/SanitizerMetadata.h
index bcad32ce31df..f5dd0e503cc0 100644
--- a/clang/lib/CodeGen/SanitizerMetadata.h
+++ b/clang/lib/CodeGen/SanitizerMetadata.h
@@ -20,7 +20,6 @@
 namespace llvm {
 class GlobalVariable;
 class Instruction;
-class MDNode;
 } // namespace llvm
 
 namespace clang {
diff --git a/clang/lib/Interpreter/IncrementalExecutor.h b/clang/lib/Interpreter/IncrementalExecutor.h
index f11ec0aa9e75..5b0f982b62dd 100644
--- a/clang/lib/Interpreter/IncrementalExecutor.h
+++ b/clang/lib/Interpreter/IncrementalExecutor.h
@@ -21,7 +21,6 @@
 
 namespace llvm {
 class Error;
-class Module;
 namespace orc {
 class LLJIT;
 class ThreadSafeContext;