Index: clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
+++ clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
@@ -45,6 +45,8 @@
       TK_AsIs,
       castExpr(anyOf(ImplicitCastToNull,
                      explicitCastExpr(hasDescendant(ImplicitCastToNull))),
+               // Skip implicit casts to 0 generated by operator<=> rewrites.
+               unless(hasAncestor(cxxRewrittenBinaryOperator())),
                unless(hasAncestor(explicitCastExpr())))
           .bind(CastSequence));
 }
Index: clang-tools-extra/test/clang-tidy/checkers/modernize-use-nullptr-cxx20.cpp
===================================================================
--- /dev/null
+++ clang-tools-extra/test/clang-tidy/checkers/modernize-use-nullptr-cxx20.cpp
@@ -0,0 +1,19 @@
+// RUN: %check_clang_tidy -std=c++20 %s modernize-use-nullptr %t
+
+#include <compare>
+
+class A {
+public:
+  auto operator<=>(const A &other) const = default;
+};
+
+void test_cxx_rewritten_binary_ops() {
+  A a1, a2;
+  bool result;
+  // should not change next line to (a1 nullptr a2)
+  result = (a1 < a2);
+  // CHECK-FIXES: result = (a1 < a2);
+  // should not change next line to (a1 nullptr a2)
+  result = (a1 >= a2);
+  // CHECK-FIXES: result = (a1 >= a2);
+}