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
@@ -7446,6 +7446,8 @@
     "duration">;
   def err_this_capture : Error<
     "'this' cannot be %select{implicitly |}0captured in this context">;
+  def note_lambda_this_capture_fixit : Note<
+    "explicitly capture 'this'">;
   def err_lambda_capture_anonymous_var : Error<
     "unnamed variable cannot be implicitly captured in a lambda expression">;
   def err_lambda_capture_flexarray_type : Error<
@@ -7454,6 +7456,10 @@
   def err_lambda_impcap : Error<
     "variable %0 cannot be implicitly captured in a lambda with no "
     "capture-default specified">;
+  def note_lambda_variable_capture_fixit : Note<
+    "capture variable %0 by %select{value|reference}1">;
+  def note_lambda_default_capture_fixit : Note<
+    "capture all by %select{value|reference}0">;
   def note_lambda_decl : Note<"lambda expression begins here">;
   def err_lambda_unevaluated_operand : Error<
     "lambda expression in an unevaluated operand">;
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -17406,6 +17406,39 @@
   return !Invalid;
 }
 
+static void buildLambdaCaptureFixit(Sema &Sema, LambdaScopeInfo *LSI,
+                                    VarDecl *Var) {
+  SmallString<32> FixBuffer;
+  StringRef Separator = LSI->NumExplicitCaptures > 0 ? ", " : "";
+  if (Var->getDeclName().isIdentifier()) {
+    SourceLocation VarInsertLoc = LSI->IntroducerRange.getEnd();
+    FixBuffer.assign({Separator, Var->getName()});
+    Sema.Diag(VarInsertLoc, diag::note_lambda_variable_capture_fixit)
+        << Var << /*value*/ 0
+        << FixItHint::CreateInsertion(VarInsertLoc, FixBuffer);
+    FixBuffer.assign({Separator, "&", Var->getName()});
+    Sema.Diag(VarInsertLoc, diag::note_lambda_variable_capture_fixit)
+        << Var << /*reference*/ 1
+        << FixItHint::CreateInsertion(VarInsertLoc, FixBuffer);
+  }
+
+  // Default capture mode must be specified first.
+  SourceLocation DefaultInsertLoc =
+      LSI->IntroducerRange.getBegin().getLocWithOffset(1);
+
+  // Can't default capture by value if this is captured before c++20.
+  if (!LSI->isCXXThisCaptured() || Sema.getLangOpts().CPlusPlus20) {
+    FixBuffer.assign({"=", Separator});
+    Sema.Diag(DefaultInsertLoc, diag::note_lambda_default_capture_fixit)
+        << /*value*/ 0
+        << FixItHint::CreateInsertion(DefaultInsertLoc, FixBuffer);
+  }
+  FixBuffer.assign({"&", Separator});
+  Sema.Diag(DefaultInsertLoc, diag::note_lambda_default_capture_fixit)
+      << /*reference*/ 1
+      << FixItHint::CreateInsertion(DefaultInsertLoc, FixBuffer);
+}
+
 bool Sema::tryCaptureVariable(
     VarDecl *Var, SourceLocation ExprLoc, TryCaptureKind Kind,
     SourceLocation EllipsisLoc, bool BuildAndDiagnose, QualType &CaptureType,
@@ -17495,6 +17528,7 @@
           Diag(ExprLoc, diag::err_lambda_impcap) << Var;
           Diag(Var->getLocation(), diag::note_previous_decl) << Var;
           Diag(LSI->Lambda->getBeginLoc(), diag::note_lambda_decl);
+          buildLambdaCaptureFixit(*this, LSI, Var);
         } else
           diagnoseUncapturableValueReference(*this, ExprLoc, Var, DC);
       }
@@ -17573,9 +17607,11 @@
       if (BuildAndDiagnose) {
         Diag(ExprLoc, diag::err_lambda_impcap) << Var;
         Diag(Var->getLocation(), diag::note_previous_decl) << Var;
-        if (cast<LambdaScopeInfo>(CSI)->Lambda)
+        if (cast<LambdaScopeInfo>(CSI)->Lambda) {
           Diag(cast<LambdaScopeInfo>(CSI)->Lambda->getBeginLoc(),
                diag::note_lambda_decl);
+          buildLambdaCaptureFixit(*this, cast<LambdaScopeInfo>(CSI), Var);
+        }
         // FIXME: If we error out because an outer lambda can not implicitly
         // capture a variable that an inner lambda explicitly captures, we
         // should have the inner lambda do the explicit capture - because
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -1226,6 +1226,14 @@
   }
 }
 
+static void buildLambdaThisCaptureFixit(Sema &Sema, LambdaScopeInfo *LSI) {
+  SourceLocation DiagLoc = LSI->IntroducerRange.getEnd();
+  assert(!LSI->isCXXThisCaptured());
+  Sema.Diag(DiagLoc, diag::note_lambda_this_capture_fixit)
+      << FixItHint::CreateInsertion(
+             DiagLoc, LSI->NumExplicitCaptures > 0 ? ", this" : "this");
+}
+
 bool Sema::CheckCXXThisCapture(SourceLocation Loc, const bool Explicit,
     bool BuildAndDiagnose, const unsigned *const FunctionScopeIndexToStopAt,
     const bool ByCopy) {
@@ -1274,9 +1282,12 @@
       LambdaScopeInfo *LSI = dyn_cast<LambdaScopeInfo>(CSI);
       if (LSI && isGenericLambdaCallOperatorSpecialization(LSI->CallOperator)) {
         // This context can't implicitly capture 'this'; fail out.
-        if (BuildAndDiagnose)
+        if (BuildAndDiagnose) {
           Diag(Loc, diag::err_this_capture)
               << (Explicit && idx == MaxFunctionScopesIndex);
+          if (!Explicit)
+            buildLambdaThisCaptureFixit(*this, LSI);
+        }
         return true;
       }
       if (CSI->ImpCaptureStyle == CapturingScopeInfo::ImpCap_LambdaByref ||
@@ -1296,6 +1307,9 @@
       if (BuildAndDiagnose)
         Diag(Loc, diag::err_this_capture)
             << (Explicit && idx == MaxFunctionScopesIndex);
+
+      if (!Explicit)
+        buildLambdaThisCaptureFixit(*this, LSI);
       return true;
     }
     break;