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
@@ -591,11 +591,13 @@
 def IntInBoolContext : DiagGroup<"int-in-bool-context">;
 def TautologicalTypeLimitCompare : DiagGroup<"tautological-type-limit-compare">;
 def TautologicalUnsignedZeroCompare : DiagGroup<"tautological-unsigned-zero-compare">;
+def TautologicalUnsignedCharZeroCompare : DiagGroup<"tautological-unsigned-char-zero-compare">;
 def TautologicalUnsignedEnumZeroCompare : DiagGroup<"tautological-unsigned-enum-zero-compare">;
 // For compatibility with GCC. Tautological comparison warnings for constants
 // that are an extremal value of the type.
 def TypeLimits : DiagGroup<"type-limits", [TautologicalTypeLimitCompare,
                                            TautologicalUnsignedZeroCompare,
+                                           TautologicalUnsignedCharZeroCompare,
                                            TautologicalUnsignedEnumZeroCompare]>;
 // Additional tautological comparison warnings based on the expression, not
 // only on its type.
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
@@ -6784,6 +6784,10 @@
   "result of comparison of %select{%3|unsigned expression}0 %2 "
   "%select{unsigned expression|%3}0 is always %4">,
   InGroup<TautologicalUnsignedZeroCompare>, DefaultIgnore;
+def warn_unsigned_char_always_true_comparison : Warning<
+  "result of comparison of %select{%3|char expression}0 %2 "
+  "%select{char expression|%3}0 is always %4, since char is interpreted as "
+  "unsigned">, InGroup<TautologicalUnsignedCharZeroCompare>, DefaultIgnore;
 def warn_unsigned_enum_always_true_comparison : Warning<
   "result of comparison of %select{%3|unsigned enum expression}0 %2 "
   "%select{unsigned enum expression|%3}0 is always %4">,
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -11415,11 +11415,14 @@
             << OtherIsBooleanDespiteType << *Result
             << E->getLHS()->getSourceRange() << E->getRHS()->getSourceRange());
   } else {
-    unsigned Diag = (isKnownToHaveUnsignedValue(OriginalOther) && Value == 0)
-                        ? (HasEnumType(OriginalOther)
-                               ? diag::warn_unsigned_enum_always_true_comparison
-                               : diag::warn_unsigned_always_true_comparison)
-                        : diag::warn_tautological_constant_compare;
+    bool IsCharTy = OtherT.withoutLocalFastQualifiers() == S.Context.CharTy;
+    unsigned Diag =
+        (isKnownToHaveUnsignedValue(OriginalOther) && Value == 0)
+            ? (HasEnumType(OriginalOther)
+                   ? diag::warn_unsigned_enum_always_true_comparison
+               : IsCharTy ? diag::warn_unsigned_char_always_true_comparison
+                          : diag::warn_unsigned_always_true_comparison)
+            : diag::warn_tautological_constant_compare;
 
     S.Diag(E->getOperatorLoc(), Diag)
         << RhsConstant << OtherT << E->getOpcodeStr() << OS.str() << *Result
diff --git a/clang/test/Sema/tautological-unsigned-char-zero-compare.cc b/clang/test/Sema/tautological-unsigned-char-zero-compare.cc
new file mode 100644
--- /dev/null
+++ b/clang/test/Sema/tautological-unsigned-char-zero-compare.cc
@@ -0,0 +1,39 @@
+// RUN: %clang_cc1 -fsyntax-only \
+// RUN:            -fno-signed-char \
+// RUN:            -Wtautological-unsigned-zero-compare \
+// RUN:            -Wtautological-unsigned-char-zero-compare \
+// RUN:            -verify=unsigned %s
+// RUN: %clang_cc1 -fsyntax-only \
+// RUN:            -Wtautological-unsigned-zero-compare \
+// RUN:            -Wtautological-unsigned-char-zero-compare \
+// RUN:            -verify=signed %s
+
+void f(char c, unsigned char uc, signed char cc) {
+  if (c < 0)
+    return;
+  // unsigned-warning@-2 {{comparison of char expression < 0 is always false, since char is interpreted as unsigned}}
+  if (uc < 0)
+    return;
+  // unsigned-warning@-2 {{comparison of unsigned expression < 0 is always false}}
+  // signed-warning@-3 {{comparison of unsigned expression < 0 is always false}}
+  if (cc < 0)
+    return;
+  // Promoted to integer expressions should not warn.
+  if (c - 4 < 0)
+    return;
+}
+
+void ref(char &c, unsigned char &uc, signed char &cc) {
+  if (c < 0)
+    return;
+  // unsigned-warning@-2 {{comparison of char expression < 0 is always false, since char is interpreted as unsigned}}
+  if (uc < 0)
+    return;
+  // unsigned-warning@-2 {{comparison of unsigned expression < 0 is always false}}
+  // signed-warning@-3 {{comparison of unsigned expression < 0 is always false}}
+  if (cc < 0)
+    return;
+  // Promoted to integer expressions should not warn.
+  if (c - 4 < 0)
+    return;
+}