diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -693,6 +693,7 @@
 def GNUZeroLineDirective : DiagGroup<"gnu-zero-line-directive">;
 def GNUZeroVariadicMacroArguments : DiagGroup<"gnu-zero-variadic-macro-arguments">;
 def Fallback : DiagGroup<"fallback">;
+def MisleadingIndentation : DiagGroup<"misleading-indentation">;
 
 // This covers both the deprecated case (in C++98)
 // and the extension case (in C++11 onwards).
@@ -884,7 +885,7 @@
 // Note that putting warnings in -Wall will not disable them by default. If a
 // warning should be active _only_ when -Wall is passed in, mark it as
 // DefaultIgnore in addition to putting it here.
-def All : DiagGroup<"all", [Most, Parentheses, Switch, SwitchBool]>;
+def All : DiagGroup<"all", [Most, Parentheses, Switch, SwitchBool, MisleadingIndentation]>;
 
 // Warnings that should be in clang-cl /w4.
 def : DiagGroup<"CL4", [All, Extra]>;
diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -61,6 +61,13 @@
   "remove unnecessary ';' to silence this warning">,
   InGroup<ExtraSemiStmt>, DefaultIgnore;
 
+def warn_misleading_indentation : Warning<
+  "misleading indentation; statement is not part of "
+  "the previous '%select{if|else|for|while|else if}0'">,
+  InGroup<MisleadingIndentation>, DefaultIgnore;
+def note_previous_statement : Note<
+  "previous statement is here">;
+
 def ext_thread_before : Extension<"'__thread' before '%0'">;
 def ext_keyword_as_ident : ExtWarn<
   "keyword '%0' will be made available as an identifier "
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -932,6 +932,12 @@
     return TheModuleLoader.HadFatalFailure;
   }
 
+  /// Retrieve the number of Directives that have been processed by the
+  /// Preprocessor.
+  unsigned getNumDirectives() const {
+    return NumDirectives;
+  }
+
   /// True if we are currently preprocessing a #if or #elif directive
   bool isParsingIfOrElifDirective() const {
     return ParsingIfOrElifDirective;
diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
--- a/clang/include/clang/Parse/Parser.h
+++ b/clang/include/clang/Parse/Parser.h
@@ -1122,6 +1122,11 @@
   /// point for skipping past a simple-declaration.
   void SkipMalformedDecl();
 
+  /// The location of the first statement inside an else that might
+  /// have a missleading indentation. If there is no
+  /// MisleadingIndentationChecker on an else active, this location is invalid.
+  SourceLocation MisleadingIndentationElseLoc;
+
 private:
   //===--------------------------------------------------------------------===//
   // Lexing and parsing of C++ inline methods.
diff --git a/clang/lib/Parse/ParseStmt.cpp b/clang/lib/Parse/ParseStmt.cpp
--- a/clang/lib/Parse/ParseStmt.cpp
+++ b/clang/lib/Parse/ParseStmt.cpp
@@ -1191,6 +1191,59 @@
   return false;
 }
 
+namespace {
+
+enum MisleadingStatementKind { MSK_if, MSK_else, MSK_for, MSK_while };
+
+struct MisleadingIndentationChecker {
+  Parser &P;
+  SourceLocation StmtLoc;
+  SourceLocation PrevLoc;
+  unsigned NumDirectives;
+  MisleadingStatementKind Kind;
+  bool NeedsChecking;
+  bool ShouldSkip;
+  MisleadingIndentationChecker(Parser &P, MisleadingStatementKind K,
+                               SourceLocation SL)
+      : P(P), StmtLoc(SL), PrevLoc(P.getCurToken().getLocation()),
+        NumDirectives(P.getPreprocessor().getNumDirectives()), Kind(K),
+        NeedsChecking(true), ShouldSkip(P.getCurToken().is(tok::l_brace)) {
+    if (!P.MisleadingIndentationElseLoc.isInvalid()) {
+      StmtLoc = P.MisleadingIndentationElseLoc;
+      P.MisleadingIndentationElseLoc = SourceLocation();
+    }
+    if (Kind == MSK_else && !ShouldSkip)
+      P.MisleadingIndentationElseLoc = SL;
+  }
+  void Check() {
+    NeedsChecking = false;
+    Token Tok = P.getCurToken();
+    if (ShouldSkip || NumDirectives != P.getPreprocessor().getNumDirectives() ||
+        Tok.isOneOf(tok::semi, tok::r_brace) || Tok.isAnnotation() ||
+        Tok.getLocation().isMacroID() || PrevLoc.isMacroID() ||
+        StmtLoc.isMacroID() ||
+        (Kind == MSK_else && P.MisleadingIndentationElseLoc.isInvalid())) {
+      P.MisleadingIndentationElseLoc = SourceLocation();
+      return;
+    }
+
+    SourceManager &SM = P.getPreprocessor().getSourceManager();
+    unsigned PrevColNum = SM.getSpellingColumnNumber(PrevLoc);
+    unsigned CurColNum = SM.getSpellingColumnNumber(Tok.getLocation());
+    unsigned StmtColNum = SM.getSpellingColumnNumber(StmtLoc);
+
+    if (PrevColNum != 0 && CurColNum != 0 && StmtColNum != 0 &&
+        ((PrevColNum > StmtColNum && PrevColNum == CurColNum) ||
+         !Tok.isAtStartOfLine()) && SM.getPresumedLineNumber(StmtLoc) !=
+          SM.getPresumedLineNumber(Tok.getLocation())) {
+      P.Diag(Tok.getLocation(), diag::warn_misleading_indentation)
+          << Kind;
+      P.Diag(StmtLoc, diag::note_previous_statement);
+    }
+  }
+};
+
+}
 
 /// ParseIfStatement
 ///       if-statement: [C99 6.8.4.1]
@@ -1265,6 +1318,8 @@
   //
   ParseScope InnerScope(this, Scope::DeclScope, C99orCXX, Tok.is(tok::l_brace));
 
+  MisleadingIndentationChecker MIChecker(*this, MSK_if, IfLoc);
+
   // Read the 'then' stmt.
   SourceLocation ThenStmtLoc = Tok.getLocation();
 
@@ -1278,6 +1333,9 @@
     ThenStmt = ParseStatement(&InnerStatementTrailingElseLoc);
   }
 
+  if (Tok.isNot(tok::kw_else))
+    MIChecker.Check();
+
   // Pop the 'if' scope if needed.
   InnerScope.Exit();
 
@@ -1305,12 +1363,17 @@
     ParseScope InnerScope(this, Scope::DeclScope, C99orCXX,
                           Tok.is(tok::l_brace));
 
+    MisleadingIndentationChecker MIChecker(*this, MSK_else, ElseLoc);
+
     EnterExpressionEvaluationContext PotentiallyDiscarded(
         Actions, Sema::ExpressionEvaluationContext::DiscardedStatement, nullptr,
         Sema::ExpressionEvaluationContextRecord::EK_Other,
         /*ShouldEnter=*/ConstexprCondition && *ConstexprCondition);
     ElseStmt = ParseStatement();
 
+    if (ElseStmt.isUsable())
+      MIChecker.Check();
+
     // Pop the 'else' scope if needed.
     InnerScope.Exit();
   } else if (Tok.is(tok::code_completion)) {
@@ -1484,9 +1547,13 @@
   //
   ParseScope InnerScope(this, Scope::DeclScope, C99orCXX, Tok.is(tok::l_brace));
 
+  MisleadingIndentationChecker MIChecker(*this, MSK_while, WhileLoc);
+
   // Read the body statement.
   StmtResult Body(ParseStatement(TrailingElseLoc));
 
+  if (Body.isUsable())
+    MIChecker.Check();
   // Pop the body scope if needed.
   InnerScope.Exit();
   WhileScope.Exit();
@@ -1918,9 +1985,14 @@
   if (C99orCXXorObjC)
     getCurScope()->decrementMSManglingNumber();
 
+  MisleadingIndentationChecker MIChecker(*this, MSK_for, ForLoc);
+
   // Read the body statement.
   StmtResult Body(ParseStatement(TrailingElseLoc));
 
+  if (Body.isUsable())
+    MIChecker.Check();
+
   // Pop the body scope if needed.
   InnerScope.Exit();
 
diff --git a/clang/test/Index/pragma-diag-reparse.c b/clang/test/Index/pragma-diag-reparse.c
--- a/clang/test/Index/pragma-diag-reparse.c
+++ b/clang/test/Index/pragma-diag-reparse.c
@@ -11,6 +11,7 @@
   return x;
 }
 
+#pragma clang diagnostic ignored "-Wmisleading-indentation"
 void foo() { int b=0; while (b==b); }
 
 // RUN: env CINDEXTEST_EDITING=1 CINDEXTEST_FAILONERROR=1 c-index-test -test-load-source-reparse 5 local \
diff --git a/clang/test/Misc/warning-wall.c b/clang/test/Misc/warning-wall.c
--- a/clang/test/Misc/warning-wall.c
+++ b/clang/test/Misc/warning-wall.c
@@ -90,6 +90,7 @@
 CHECK-NEXT:    -Wdangling-else
 CHECK-NEXT:  -Wswitch
 CHECK-NEXT:  -Wswitch-bool
+CHECK-NEXT:  -Wmisleading-indentation
 
 
 CHECK-NOT:-W
diff --git a/clang/test/Parser/warn-misleading-indentation.cpp b/clang/test/Parser/warn-misleading-indentation.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Parser/warn-misleading-indentation.cpp
@@ -0,0 +1,208 @@
+// RUN: %clang_cc1 -x c -fsyntax-only -verify %s
+// RUN: %clang_cc1 -x c -fsyntax-only -verify -Wmisleading-indentation -DWITH_WARN %s
+// RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify -Wall -Wno-unused -DWITH_WARN -DCXX17 %s
+// RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify -Wall -Wno-unused -Wno-misleading-indentation -DCXX17 %s
+
+#ifndef WITH_WARN
+// expected-no-diagnostics
+#endif
+
+void f0(int i) {
+  if (i)
+#ifdef WITH_WARN
+// expected-note@-2 {{here}}
+#endif
+    i = i + 1;
+    int x = 0;
+#ifdef WITH_WARN
+// expected-warning@-2 {{misleading indentation; statement is not part of the previous 'if'}}
+#endif
+  return;
+#ifdef CXX17
+  if constexpr (false)
+#ifdef WITH_WARN
+// expected-note@-2 {{here}}
+#endif
+    i = 0;
+    i += 1;
+#ifdef WITH_WARN
+// expected-warning@-2 {{misleading indentation; statement is not part of the previous 'if'}}
+#endif
+#endif
+}
+
+void f1(int i) {
+  for (;i;)
+#ifdef WITH_WARN
+// expected-note@-2 {{here}}
+#endif
+    i = i + 1;
+    i *= 2;
+#ifdef WITH_WARN
+// expected-warning@-2 {{misleading indentation; statement is not part of the previous 'for'}}
+#endif
+  return;
+}
+
+void f2(int i) {
+  while (i)
+#ifdef WITH_WARN
+// expected-note@-2 {{here}}
+#endif
+    i = i + 1; i *= 2;
+#ifdef WITH_WARN
+// expected-warning@-2 {{misleading indentation; statement is not part of the previous 'while'}}
+#endif
+  return;
+}
+
+void f3(int i) {
+  if (i)
+    i = i + 1;
+  else
+#ifdef WITH_WARN
+// expected-note@-2 {{here}}
+#endif
+    i *= 2;
+    const int x = 0;
+#ifdef WITH_WARN
+// expected-warning@-2 {{misleading indentation; statement is not part of the previous 'else'}}
+#endif
+}
+
+#ifdef CXX17
+struct Range {
+  int *begin() {return nullptr;}
+  int *end() {return nullptr;}
+};
+#endif
+
+void f4(int i) {
+  if (i)
+  i *= 2;
+  return;
+  if (i)
+    i *= 2;
+    ;
+  if (i)
+#ifdef WITH_WARN
+// expected-note@-2 {{here}}
+#endif
+    i *= 2;
+    typedef int Int;
+#ifdef WITH_WARN
+// expected-warning@-2 {{misleading indentation; statement is not part of the previous 'if'}}
+#endif
+#ifdef CXX17
+  Range R;
+  for (auto e : R)
+#ifdef WITH_WARN
+// expected-note@-2 {{here}}
+#endif
+    i *= 2;
+    using Int2 = int;
+#ifdef WITH_WARN
+// expected-warning@-2 {{misleading indentation; statement is not part of the previous 'for'}}
+#endif
+#endif
+}
+
+int bar(void);
+
+int foo(int* dst)
+{   
+    if (dst)
+       return
+    bar();
+  if (dst)
+    dst = dst + \
+    bar();
+  return 0;
+}
+
+void g(int i) {
+  if (1)
+    i = 2;
+  else
+         if (i == 3)
+#ifdef WITH_WARN
+// expected-note@-3 {{here}}
+#endif
+    i = 4;
+    i = 5;
+#ifdef WITH_WARN
+// expected-warning@-2 {{misleading indentation; statement is not part of the previous 'if'}}
+#endif
+}
+
+// Or this
+#define TEST i = 5
+void g0(int i) {
+  if (1)
+    i = 2;
+  else
+    i = 5;
+    TEST;
+}
+
+void g1(int i) {
+  if (1)
+    i = 2;
+  else if (i == 3)
+#ifdef WITH_WARN
+// expected-note@-2 {{here}}
+#endif
+      i = 4;
+      i = 5;
+#ifdef WITH_WARN
+// expected-warning@-2 {{misleading indentation; statement is not part of the previous 'if'}}
+#endif
+}
+
+void g2(int i) {
+  if (1)
+    i = 2;
+  else
+    if (i == 3)
+    {i = 4;}
+    i = 5;
+}
+
+void g6(int i) {
+        if (1)
+                if (i == 3)
+#ifdef WITH_WARN
+// expected-note@-2 {{here}}
+#endif
+                        i = 4;
+                        i = 5;
+#ifdef WITH_WARN
+// expected-warning@-2 {{misleading indentation; statement is not part of the previous 'if'}}
+#endif
+}
+
+void g7(int i) {
+  if (1)
+    i = 4;
+#ifdef TEST1
+#endif
+    i = 5;
+}
+
+void a1(int i) { if (1) i = 4; return; }
+
+void a2(int i) {
+  {
+    if (1)
+      i = 4;
+      }
+  return;
+}
+
+void a3(int i) {
+  if (1)
+    {
+    i = 4;
+    }
+    return;
+}
\ No newline at end of file
diff --git a/clang/test/Preprocessor/pragma_diagnostic_sections.cpp b/clang/test/Preprocessor/pragma_diagnostic_sections.cpp
--- a/clang/test/Preprocessor/pragma_diagnostic_sections.cpp
+++ b/clang/test/Preprocessor/pragma_diagnostic_sections.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -Wall -Wunused-macros -Wunused-parameter -Wno-uninitialized -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wall -Wunused-macros -Wunused-parameter -Wno-uninitialized -Wno-misleading-indentation -verify %s
 
 // rdar://8365684
 struct S {