diff --git a/libcxx/include/__concepts/swappable.h b/libcxx/include/__concepts/swappable.h
--- a/libcxx/include/__concepts/swappable.h
+++ b/libcxx/include/__concepts/swappable.h
@@ -9,6 +9,7 @@
 #ifndef _LIBCPP___CONCEPTS_SWAPPABLE_H
 #define _LIBCPP___CONCEPTS_SWAPPABLE_H
 
+#include <__algorithm/ranges_swap_ranges.h>
 #include <__concepts/assignable.h>
 #include <__concepts/class_or_enum.h>
 #include <__concepts/common_reference_with.h>
@@ -75,10 +76,13 @@
     constexpr void operator()(_Tp(& __t)[_Size], _Up(& __u)[_Size]) const
       noexcept(noexcept((*this)(*__t, *__u)))
     {
-      // TODO(cjdb): replace with `ranges::swap_ranges`.
+#if defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
       for (size_t __i = 0; __i < _Size; ++__i) {
         (*this)(__t[__i], __u[__i]);
       }
+#else
+      ranges::swap_ranges(__t, __u);
+#endif
     }
 
     // 2.3   Otherwise, if `E1` and `E2` are lvalues of the same type `T` that models...