diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -198,6 +198,10 @@
 - Update ``FunctionDeclBitfields.NumFunctionDeclBits``. This fixes:
   (`#64171 <https://github.com/llvm/llvm-project/issues/64171>`_).
 
+- Correctly parse ``(T())(pack...)`` as a call to ``T::operator()``
+  instead of an invalid cast expression.
+  (`#64926 <https://github.com/llvm/llvm-project/issues/64926>`_)
+
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 - Fixed an import failure of recursive friend class template.
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
@@ -245,6 +245,10 @@
   /// should not be set directly.
   bool InMessageExpression;
 
+  /// Track whether we are currently trying to parse an ambiguous
+  /// paren expression after a cast expression.
+  bool InAmbiguousCXXParenExprParsing;
+
   /// Gets set to true after calling ProduceSignatureHelp, it is for a
   /// workaround to make sure ProduceSignatureHelp is only called at the deepest
   /// function call.
diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -28,6 +28,7 @@
 #include "clang/Parse/RAIIObjectsForParser.h"
 #include "clang/Sema/DeclSpec.h"
 #include "clang/Sema/EnterExpressionEvaluationContext.h"
+#include "clang/Sema/Ownership.h"
 #include "clang/Sema/ParsedTemplate.h"
 #include "clang/Sema/Scope.h"
 #include "clang/Sema/TypoCorrection.h"
@@ -3164,6 +3165,14 @@
         return ParseFoldExpression(ArgExprs[0], T);
       }
 
+      // If we find an ellipsis, this cannot be part of a cast expression,
+      // stop there and try to parse a simple expression instead.
+      // This handles `(T())(expr...)`.
+      if(InAmbiguousCXXParenExprParsing && isTypeCast && Tok.is(tok::ellipsis)
+          && ExprType == Parser::CastExpr && getLangOpts().CPlusPlus) {
+        return ExprError();
+      }
+
       ExprType = SimpleExpr;
       Result = Actions.ActOnParenListExpr(OpenLoc, Tok.getLocation(),
                                           ArgExprs);
diff --git a/clang/lib/Parse/ParseExprCXX.cpp b/clang/lib/Parse/ParseExprCXX.cpp
--- a/clang/lib/Parse/ParseExprCXX.cpp
+++ b/clang/lib/Parse/ParseExprCXX.cpp
@@ -3981,6 +3981,7 @@
       // If it is not a cast-expression, NotCastExpr will be true and no token
       // will be consumed.
       ColonProt.restore();
+      SaveAndRestore AmbiguousParenRAII(InAmbiguousCXXParenExprParsing, true);
       Result = ParseCastExpression(AnyCastExpr,
                                    false/*isAddressofOperand*/,
                                    NotCastExpr,
diff --git a/clang/lib/Parse/Parser.cpp b/clang/lib/Parse/Parser.cpp
--- a/clang/lib/Parse/Parser.cpp
+++ b/clang/lib/Parse/Parser.cpp
@@ -53,6 +53,7 @@
     : PP(pp), PreferredType(pp.isCodeCompletionEnabled()), Actions(actions),
       Diags(PP.getDiagnostics()), GreaterThanIsOperator(true),
       ColonIsSacred(false), InMessageExpression(false),
+      InAmbiguousCXXParenExprParsing(false),
       TemplateParameterDepth(0), ParsingInObjCContainer(false) {
   SkipFunctionBodies = pp.isCodeCompletionEnabled() || skipFunctionBodies;
   Tok.startToken();
diff --git a/clang/test/Parser/cxx-ambig-paren-expr.cpp b/clang/test/Parser/cxx-ambig-paren-expr.cpp
--- a/clang/test/Parser/cxx-ambig-paren-expr.cpp
+++ b/clang/test/Parser/cxx-ambig-paren-expr.cpp
@@ -70,3 +70,24 @@
     return;
 }
 
+namespace GH64926 {
+template<typename T, typename... Args>
+void PackInAmbiguousCastExpression(Args... args) {
+	  (void) (Args::foo()...); // expected-error {{expression contains unexpanded parameter pack 'Args'}} \
+                            // expected-error {{expected ')'}} expected-note {{to match this '('}}
+
+    (void) (args...);  // expected-error {{expression contains unexpanded parameter pack 'args'}} \
+                       // expected-error {{expected ')'}} expected-note {{to match this '('}}
+
+    (void) (((args))...);  // expected-error {{expression contains unexpanded parameter pack 'args'}} \
+                           // expected-error {{expected ')'}} expected-note {{to match this '('}}
+
+    (void) (((args...)));  // expected-error {{expression contains unexpanded parameter pack 'args'}} \
+                           // expected-error {{expected ')'}} expected-note {{to match this '('}}
+    (T()) (Args::foo()...);
+    (T()) (args...);
+    (T()) (((args))...);
+    (T()) (((args...))); // expected-error {{expression contains unexpanded parameter pack 'args'}} \
+                         // expected-error {{expected ')'}} expected-note {{to match this '('}}
+}
+}