diff --git a/libcxx/include/__algorithm/binary_search.h b/libcxx/include/__algorithm/binary_search.h
--- a/libcxx/include/__algorithm/binary_search.h
+++ b/libcxx/include/__algorithm/binary_search.h
@@ -37,8 +37,7 @@
 bool
 binary_search(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value)
 {
-    return std::binary_search(__first, __last, __value,
-                              __less<typename iterator_traits<_ForwardIterator>::value_type, _Tp>());
+    return std::binary_search(__first, __last, __value, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/clamp.h b/libcxx/include/__algorithm/clamp.h
--- a/libcxx/include/__algorithm/clamp.h
+++ b/libcxx/include/__algorithm/clamp.h
@@ -37,7 +37,7 @@
 const _Tp&
 clamp(const _Tp& __v, const _Tp& __lo, const _Tp& __hi)
 {
-    return _VSTD::clamp(__v, __lo, __hi, __less<_Tp>());
+    return _VSTD::clamp(__v, __lo, __hi, __less<>());
 }
 #endif
 
diff --git a/libcxx/include/__algorithm/comp.h b/libcxx/include/__algorithm/comp.h
--- a/libcxx/include/__algorithm/comp.h
+++ b/libcxx/include/__algorithm/comp.h
@@ -29,41 +29,17 @@
 template <class _Lhs, class _Rhs>
 struct __is_trivial_equality_predicate<__equal_to, _Lhs, _Rhs> : true_type {};
 
-template <class _T1, class _T2 = _T1>
-struct __less
-{
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX14
-    bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
-
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX14
-    bool operator()(const _T1& __x, const _T2& __y) const {return __x < __y;}
-
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX14
-    bool operator()(const _T2& __x, const _T1& __y) const {return __x < __y;}
-
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX14
-    bool operator()(const _T2& __x, const _T2& __y) const {return __x < __y;}
-};
-
-template <class _T1>
-struct __less<_T1, _T1>
-{
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX14
-    bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
-};
-
-template <class _T1>
-struct __less<const _T1, _T1>
-{
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX14
-    bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
-};
-
-template <class _T1>
-struct __less<_T1, const _T1>
-{
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX14
-    bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
+// The definition is required because __less is part of the ABI, but it's empty
+// because all comparisons should be transparent.
+template <class _T1 = void, class _T2 = _T1>
+struct __less {};
+
+template <>
+struct __less<void, void> {
+  template <class _Tp, class _Up>
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool operator()(const _Tp& __lhs, const _Up& __rhs) const {
+    return __lhs < __rhs;
+  }
 };
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/equal_range.h b/libcxx/include/__algorithm/equal_range.h
--- a/libcxx/include/__algorithm/equal_range.h
+++ b/libcxx/include/__algorithm/equal_range.h
@@ -75,11 +75,7 @@
 template <class _ForwardIterator, class _Tp>
 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_ForwardIterator, _ForwardIterator>
 equal_range(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
-  return std::equal_range(
-      std::move(__first),
-      std::move(__last),
-      __value,
-      __less<typename iterator_traits<_ForwardIterator>::value_type, _Tp>());
+  return std::equal_range(std::move(__first), std::move(__last), __value, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/includes.h b/libcxx/include/__algorithm/includes.h
--- a/libcxx/include/__algorithm/includes.h
+++ b/libcxx/include/__algorithm/includes.h
@@ -61,13 +61,7 @@
 template <class _InputIterator1, class _InputIterator2>
 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
 includes(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2) {
-  return std::includes(
-      std::move(__first1),
-      std::move(__last1),
-      std::move(__first2),
-      std::move(__last2),
-      __less<typename iterator_traits<_InputIterator1>::value_type,
-             typename iterator_traits<_InputIterator2>::value_type>());
+  return std::includes(std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2), __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/inplace_merge.h b/libcxx/include/__algorithm/inplace_merge.h
--- a/libcxx/include/__algorithm/inplace_merge.h
+++ b/libcxx/include/__algorithm/inplace_merge.h
@@ -246,8 +246,7 @@
 void
 inplace_merge(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last)
 {
-    std::inplace_merge(std::move(__first), std::move(__middle), std::move(__last),
-                        __less<typename iterator_traits<_BidirectionalIterator>::value_type>());
+    std::inplace_merge(std::move(__first), std::move(__middle), std::move(__last), __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/is_heap.h b/libcxx/include/__algorithm/is_heap.h
--- a/libcxx/include/__algorithm/is_heap.h
+++ b/libcxx/include/__algorithm/is_heap.h
@@ -36,7 +36,7 @@
 bool
 is_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
 {
-    return _VSTD::is_heap(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
+    return _VSTD::is_heap(__first, __last, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/is_heap_until.h b/libcxx/include/__algorithm/is_heap_until.h
--- a/libcxx/include/__algorithm/is_heap_until.h
+++ b/libcxx/include/__algorithm/is_heap_until.h
@@ -58,7 +58,7 @@
 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _RandomAccessIterator
 is_heap_until(_RandomAccessIterator __first, _RandomAccessIterator __last)
 {
-    return _VSTD::__is_heap_until(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
+    return _VSTD::__is_heap_until(__first, __last, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/is_sorted.h b/libcxx/include/__algorithm/is_sorted.h
--- a/libcxx/include/__algorithm/is_sorted.h
+++ b/libcxx/include/__algorithm/is_sorted.h
@@ -36,7 +36,7 @@
 bool
 is_sorted(_ForwardIterator __first, _ForwardIterator __last)
 {
-    return _VSTD::is_sorted(__first, __last, __less<typename iterator_traits<_ForwardIterator>::value_type>());
+    return _VSTD::is_sorted(__first, __last, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/is_sorted_until.h b/libcxx/include/__algorithm/is_sorted_until.h
--- a/libcxx/include/__algorithm/is_sorted_until.h
+++ b/libcxx/include/__algorithm/is_sorted_until.h
@@ -48,7 +48,7 @@
 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
 is_sorted_until(_ForwardIterator __first, _ForwardIterator __last)
 {
-    return _VSTD::is_sorted_until(__first, __last, __less<typename iterator_traits<_ForwardIterator>::value_type>());
+    return _VSTD::is_sorted_until(__first, __last, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/lexicographical_compare.h b/libcxx/include/__algorithm/lexicographical_compare.h
--- a/libcxx/include/__algorithm/lexicographical_compare.h
+++ b/libcxx/include/__algorithm/lexicographical_compare.h
@@ -52,9 +52,7 @@
 lexicographical_compare(_InputIterator1 __first1, _InputIterator1 __last1,
                         _InputIterator2 __first2, _InputIterator2 __last2)
 {
-    return _VSTD::lexicographical_compare(__first1, __last1, __first2, __last2,
-                                         __less<typename iterator_traits<_InputIterator1>::value_type,
-                                                typename iterator_traits<_InputIterator2>::value_type>());
+    return _VSTD::lexicographical_compare(__first1, __last1, __first2, __last2, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/lower_bound.h b/libcxx/include/__algorithm/lower_bound.h
--- a/libcxx/include/__algorithm/lower_bound.h
+++ b/libcxx/include/__algorithm/lower_bound.h
@@ -58,8 +58,7 @@
 template <class _ForwardIterator, class _Tp>
 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 _ForwardIterator lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
-  return std::lower_bound(__first, __last, __value,
-                          __less<typename iterator_traits<_ForwardIterator>::value_type, _Tp>());
+  return std::lower_bound(__first, __last, __value, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/make_heap.h b/libcxx/include/__algorithm/make_heap.h
--- a/libcxx/include/__algorithm/make_heap.h
+++ b/libcxx/include/__algorithm/make_heap.h
@@ -47,8 +47,7 @@
 template <class _RandomAccessIterator>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 void make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last) {
-  std::make_heap(std::move(__first), std::move(__last),
-      __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
+  std::make_heap(std::move(__first), std::move(__last), __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/max.h b/libcxx/include/__algorithm/max.h
--- a/libcxx/include/__algorithm/max.h
+++ b/libcxx/include/__algorithm/max.h
@@ -39,7 +39,7 @@
 const _Tp&
 max(_LIBCPP_LIFETIMEBOUND const _Tp& __a, _LIBCPP_LIFETIMEBOUND const _Tp& __b)
 {
-    return _VSTD::max(__a, __b, __less<_Tp>());
+    return _VSTD::max(__a, __b, __less<>());
 }
 
 #ifndef _LIBCPP_CXX03_LANG
@@ -59,7 +59,7 @@
 _Tp
 max(initializer_list<_Tp> __t)
 {
-    return *_VSTD::max_element(__t.begin(), __t.end(), __less<_Tp>());
+    return *_VSTD::max_element(__t.begin(), __t.end(), __less<>());
 }
 
 #endif // _LIBCPP_CXX03_LANG
diff --git a/libcxx/include/__algorithm/max_element.h b/libcxx/include/__algorithm/max_element.h
--- a/libcxx/include/__algorithm/max_element.h
+++ b/libcxx/include/__algorithm/max_element.h
@@ -48,8 +48,7 @@
 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator
 max_element(_ForwardIterator __first, _ForwardIterator __last)
 {
-    return _VSTD::max_element(__first, __last,
-              __less<typename iterator_traits<_ForwardIterator>::value_type>());
+    return _VSTD::max_element(__first, __last, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/merge.h b/libcxx/include/__algorithm/merge.h
--- a/libcxx/include/__algorithm/merge.h
+++ b/libcxx/include/__algorithm/merge.h
@@ -60,9 +60,7 @@
 merge(_InputIterator1 __first1, _InputIterator1 __last1,
       _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result)
 {
-    typedef typename iterator_traits<_InputIterator1>::value_type __v1;
-    typedef typename iterator_traits<_InputIterator2>::value_type __v2;
-    return _VSTD::merge(__first1, __last1, __first2, __last2, __result, __less<__v1, __v2>());
+    return _VSTD::merge(__first1, __last1, __first2, __last2, __result, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/min.h b/libcxx/include/__algorithm/min.h
--- a/libcxx/include/__algorithm/min.h
+++ b/libcxx/include/__algorithm/min.h
@@ -39,7 +39,7 @@
 const _Tp&
 min(_LIBCPP_LIFETIMEBOUND const _Tp& __a, _LIBCPP_LIFETIMEBOUND const _Tp& __b)
 {
-    return _VSTD::min(__a, __b, __less<_Tp>());
+    return _VSTD::min(__a, __b, __less<>());
 }
 
 #ifndef _LIBCPP_CXX03_LANG
@@ -59,7 +59,7 @@
 _Tp
 min(initializer_list<_Tp> __t)
 {
-    return *_VSTD::min_element(__t.begin(), __t.end(), __less<_Tp>());
+    return *_VSTD::min_element(__t.begin(), __t.end(), __less<>());
 }
 
 #endif // _LIBCPP_CXX03_LANG
diff --git a/libcxx/include/__algorithm/min_element.h b/libcxx/include/__algorithm/min_element.h
--- a/libcxx/include/__algorithm/min_element.h
+++ b/libcxx/include/__algorithm/min_element.h
@@ -61,8 +61,7 @@
 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator
 min_element(_ForwardIterator __first, _ForwardIterator __last)
 {
-    return _VSTD::min_element(__first, __last,
-              __less<typename iterator_traits<_ForwardIterator>::value_type>());
+    return _VSTD::min_element(__first, __last, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/minmax.h b/libcxx/include/__algorithm/minmax.h
--- a/libcxx/include/__algorithm/minmax.h
+++ b/libcxx/include/__algorithm/minmax.h
@@ -39,7 +39,7 @@
 pair<const _Tp&, const _Tp&>
 minmax(_LIBCPP_LIFETIMEBOUND const _Tp& __a, _LIBCPP_LIFETIMEBOUND const _Tp& __b)
 {
-    return std::minmax(__a, __b, __less<_Tp>());
+    return std::minmax(__a, __b, __less<>());
 }
 
 #ifndef _LIBCPP_CXX03_LANG
@@ -59,7 +59,7 @@
 pair<_Tp, _Tp>
 minmax(initializer_list<_Tp> __t)
 {
-    return std::minmax(__t, __less<_Tp>());
+    return std::minmax(__t, __less<>());
 }
 
 #endif // _LIBCPP_CXX03_LANG
diff --git a/libcxx/include/__algorithm/minmax_element.h b/libcxx/include/__algorithm/minmax_element.h
--- a/libcxx/include/__algorithm/minmax_element.h
+++ b/libcxx/include/__algorithm/minmax_element.h
@@ -94,7 +94,7 @@
 template <class _ForwardIterator>
 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
 pair<_ForwardIterator, _ForwardIterator> minmax_element(_ForwardIterator __first, _ForwardIterator __last) {
-    return std::minmax_element(__first, __last, __less<typename iterator_traits<_ForwardIterator>::value_type>());
+    return std::minmax_element(__first, __last, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/next_permutation.h b/libcxx/include/__algorithm/next_permutation.h
--- a/libcxx/include/__algorithm/next_permutation.h
+++ b/libcxx/include/__algorithm/next_permutation.h
@@ -69,8 +69,7 @@
 bool
 next_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last)
 {
-    return _VSTD::next_permutation(__first, __last,
-                                  __less<typename iterator_traits<_BidirectionalIterator>::value_type>());
+    return _VSTD::next_permutation(__first, __last, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/nth_element.h b/libcxx/include/__algorithm/nth_element.h
--- a/libcxx/include/__algorithm/nth_element.h
+++ b/libcxx/include/__algorithm/nth_element.h
@@ -249,8 +249,7 @@
 template <class _RandomAccessIterator>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 void nth_element(_RandomAccessIterator __first, _RandomAccessIterator __nth, _RandomAccessIterator __last) {
-  std::nth_element(std::move(__first), std::move(__nth), std::move(__last), __less<typename
-      iterator_traits<_RandomAccessIterator>::value_type>());
+  std::nth_element(std::move(__first), std::move(__nth), std::move(__last), __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/partial_sort.h b/libcxx/include/__algorithm/partial_sort.h
--- a/libcxx/include/__algorithm/partial_sort.h
+++ b/libcxx/include/__algorithm/partial_sort.h
@@ -88,8 +88,7 @@
 void
 partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last)
 {
-    _VSTD::partial_sort(__first, __middle, __last,
-                        __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
+    _VSTD::partial_sort(__first, __middle, __last, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/partial_sort_copy.h b/libcxx/include/__algorithm/partial_sort_copy.h
--- a/libcxx/include/__algorithm/partial_sort_copy.h
+++ b/libcxx/include/__algorithm/partial_sort_copy.h
@@ -79,8 +79,7 @@
 partial_sort_copy(_InputIterator __first, _InputIterator __last,
                   _RandomAccessIterator __result_first, _RandomAccessIterator __result_last)
 {
-    return _VSTD::partial_sort_copy(__first, __last, __result_first, __result_last,
-                                   __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
+    return _VSTD::partial_sort_copy(__first, __last, __result_first, __result_last, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/pop_heap.h b/libcxx/include/__algorithm/pop_heap.h
--- a/libcxx/include/__algorithm/pop_heap.h
+++ b/libcxx/include/__algorithm/pop_heap.h
@@ -65,8 +65,7 @@
 template <class _RandomAccessIterator>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 void pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last) {
-  std::pop_heap(std::move(__first), std::move(__last),
-      __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
+  std::pop_heap(std::move(__first), std::move(__last), __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/prev_permutation.h b/libcxx/include/__algorithm/prev_permutation.h
--- a/libcxx/include/__algorithm/prev_permutation.h
+++ b/libcxx/include/__algorithm/prev_permutation.h
@@ -70,8 +70,7 @@
 bool
 prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last)
 {
-    return _VSTD::prev_permutation(__first, __last,
-                                  __less<typename iterator_traits<_BidirectionalIterator>::value_type>());
+    return _VSTD::prev_permutation(__first, __last, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/push_heap.h b/libcxx/include/__algorithm/push_heap.h
--- a/libcxx/include/__algorithm/push_heap.h
+++ b/libcxx/include/__algorithm/push_heap.h
@@ -69,8 +69,7 @@
 template <class _RandomAccessIterator>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 void push_heap(_RandomAccessIterator __first, _RandomAccessIterator __last) {
-  std::push_heap(std::move(__first), std::move(__last),
-      __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
+  std::push_heap(std::move(__first), std::move(__last), __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/set_difference.h b/libcxx/include/__algorithm/set_difference.h
--- a/libcxx/include/__algorithm/set_difference.h
+++ b/libcxx/include/__algorithm/set_difference.h
@@ -66,14 +66,7 @@
     _InputIterator2 __first2,
     _InputIterator2 __last2,
     _OutputIterator __result) {
-  return std::__set_difference<_ClassicAlgPolicy>(
-      __first1,
-      __last1,
-      __first2,
-      __last2,
-      __result,
-      __less<typename iterator_traits<_InputIterator1>::value_type,
-             typename iterator_traits<_InputIterator2>::value_type>()).second;
+  return std::__set_difference<_ClassicAlgPolicy>(__first1, __last1, __first2, __last2, __result, __less<>()).second;
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/set_intersection.h b/libcxx/include/__algorithm/set_intersection.h
--- a/libcxx/include/__algorithm/set_intersection.h
+++ b/libcxx/include/__algorithm/set_intersection.h
@@ -89,8 +89,7 @@
              std::move(__first2),
              std::move(__last2),
              std::move(__result),
-             __less<typename iterator_traits<_InputIterator1>::value_type,
-                    typename iterator_traits<_InputIterator2>::value_type>())
+             __less<>())
       .__out_;
 }
 
diff --git a/libcxx/include/__algorithm/set_symmetric_difference.h b/libcxx/include/__algorithm/set_symmetric_difference.h
--- a/libcxx/include/__algorithm/set_symmetric_difference.h
+++ b/libcxx/include/__algorithm/set_symmetric_difference.h
@@ -96,8 +96,7 @@
       std::move(__first2),
       std::move(__last2),
       std::move(__result),
-      __less<typename iterator_traits<_InputIterator1>::value_type,
-             typename iterator_traits<_InputIterator2>::value_type>());
+      __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/set_union.h b/libcxx/include/__algorithm/set_union.h
--- a/libcxx/include/__algorithm/set_union.h
+++ b/libcxx/include/__algorithm/set_union.h
@@ -92,8 +92,7 @@
       std::move(__first2),
       std::move(__last2),
       std::move(__result),
-      __less<typename iterator_traits<_InputIterator1>::value_type,
-             typename iterator_traits<_InputIterator2>::value_type>());
+      __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/sort.h b/libcxx/include/__algorithm/sort.h
--- a/libcxx/include/__algorithm/sort.h
+++ b/libcxx/include/__algorithm/sort.h
@@ -124,8 +124,8 @@
 // The comparator being simple is a prerequisite for using the branchless optimization.
 template <class _Tp>
 struct __is_simple_comparator : false_type {};
-template <class _Tp>
-struct __is_simple_comparator<__less<_Tp>&> : true_type {};
+template <>
+struct __is_simple_comparator<__less<>&> : true_type {};
 template <class _Tp>
 struct __is_simple_comparator<less<_Tp>&> : true_type {};
 template <class _Tp>
@@ -885,7 +885,8 @@
     long double>;
 
 template <class _AlgPolicy, class _Type, __enable_if_t<__sort_is_specialized_in_library<_Type>::value, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void __sort_dispatch(_Type* __first, _Type* __last, __less<_Type>& __comp) {
+_LIBCPP_HIDE_FROM_ABI void __sort_dispatch(_Type* __first, _Type* __last, __less<>&) {
+  __less<_Type> __comp;
   std::__sort<__less<_Type>&, _Type*>(__first, __last, __comp);
 }
 
@@ -934,7 +935,7 @@
 template <class _RandomAccessIterator>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 void sort(_RandomAccessIterator __first, _RandomAccessIterator __last) {
-  std::sort(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
+  std::sort(__first, __last, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/sort_heap.h b/libcxx/include/__algorithm/sort_heap.h
--- a/libcxx/include/__algorithm/sort_heap.h
+++ b/libcxx/include/__algorithm/sort_heap.h
@@ -50,8 +50,7 @@
 template <class _RandomAccessIterator>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 void sort_heap(_RandomAccessIterator __first, _RandomAccessIterator __last) {
-  std::sort_heap(std::move(__first), std::move(__last),
-      __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
+  std::sort_heap(std::move(__first), std::move(__last), __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/stable_sort.h b/libcxx/include/__algorithm/stable_sort.h
--- a/libcxx/include/__algorithm/stable_sort.h
+++ b/libcxx/include/__algorithm/stable_sort.h
@@ -272,7 +272,7 @@
 template <class _RandomAccessIterator>
 inline _LIBCPP_HIDE_FROM_ABI
 void stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last) {
-  std::stable_sort(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
+  std::stable_sort(__first, __last, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/upper_bound.h b/libcxx/include/__algorithm/upper_bound.h
--- a/libcxx/include/__algorithm/upper_bound.h
+++ b/libcxx/include/__algorithm/upper_bound.h
@@ -47,8 +47,7 @@
 template <class _ForwardIterator, class _Tp, class _Compare>
 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
 upper_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value, _Compare __comp) {
-  static_assert(is_copy_constructible<_ForwardIterator>::value,
-                "Iterator has to be copy constructible");
+  static_assert(is_copy_constructible<_ForwardIterator>::value, "Iterator has to be copy constructible");
   return std::__upper_bound<_ClassicAlgPolicy>(
       std::move(__first), std::move(__last), __value, std::move(__comp), std::__identity());
 }
@@ -56,11 +55,7 @@
 template <class _ForwardIterator, class _Tp>
 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
 upper_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
-  return std::upper_bound(
-      std::move(__first),
-      std::move(__last),
-      __value,
-      __less<_Tp, typename iterator_traits<_ForwardIterator>::value_type>());
+  return std::upper_bound(std::move(__first), std::move(__last), __value, __less<>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/forward_list b/libcxx/include/forward_list
--- a/libcxx/include/forward_list
+++ b/libcxx/include/forward_list
@@ -865,18 +865,18 @@
     _LIBCPP_HIDE_FROM_ABI __remove_return_type unique(_BinaryPredicate __binary_pred);
 #ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
-    void merge(forward_list&& __x) {merge(__x, __less<value_type>());}
+    void merge(forward_list&& __x) {merge(__x, __less<>());}
     template <class _Compare>
         _LIBCPP_INLINE_VISIBILITY
         void merge(forward_list&& __x, _Compare __comp)
         {merge(__x, _VSTD::move(__comp));}
 #endif // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
-    void merge(forward_list& __x) {merge(__x, __less<value_type>());}
+    void merge(forward_list& __x) {merge(__x, __less<>());}
     template <class _Compare>
     _LIBCPP_HIDE_FROM_ABI void merge(forward_list& __x, _Compare __comp);
     _LIBCPP_INLINE_VISIBILITY
-    void sort() {sort(__less<value_type>());}
+    void sort() {sort(__less<>());}
     template <class _Compare> _LIBCPP_INLINE_VISIBILITY void sort(_Compare __comp);
     _LIBCPP_HIDE_FROM_ABI void reverse() _NOEXCEPT;
 
diff --git a/libcxx/include/list b/libcxx/include/list
--- a/libcxx/include/list
+++ b/libcxx/include/list
@@ -2101,7 +2101,7 @@
 void
 list<_Tp, _Alloc>::merge(list& __c)
 {
-    merge(__c, __less<value_type>());
+    merge(__c, __less<>());
 }
 
 template <class _Tp, class _Alloc>
@@ -2163,7 +2163,7 @@
 void
 list<_Tp, _Alloc>::sort()
 {
-    sort(__less<value_type>());
+    sort(__less<>());
 }
 
 template <class _Tp, class _Alloc>
diff --git a/libcxx/src/algorithm.cpp b/libcxx/src/algorithm.cpp
--- a/libcxx/src/algorithm.cpp
+++ b/libcxx/src/algorithm.cpp
@@ -19,9 +19,10 @@
   // that the default comparator is in use so that we are sure that there are no
   // branches in the comparator.
   std::__introsort<_ClassicAlgPolicy,
-                   Comp&,
+                   ranges::less,
                    RandomAccessIterator,
-                   __use_branchless_sort<Comp, RandomAccessIterator>::value>(first, last, comp, depth_limit);
+                   __use_branchless_sort<ranges::less, RandomAccessIterator>::value>(
+      first, last, ranges::less{}, depth_limit);
 }
 
 // clang-format off
diff --git a/libcxx/test/libcxx/algorithms/robust_against_using_non_transparent_comparators.pass.cpp b/libcxx/test/libcxx/algorithms/robust_against_using_non_transparent_comparators.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/algorithms/robust_against_using_non_transparent_comparators.pass.cpp
@@ -0,0 +1,77 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <algorithm>
+#include <cassert>
+#include <iterator>
+
+#include "test_macros.h"
+
+template <class T>
+struct Iterator {
+  using value_type        = T;
+  using pointer           = value_type*;
+  using difference_type   = std::ptrdiff_t;
+  using iterator_category = std::forward_iterator_tag;
+  struct reference {
+    T* ptr_;
+
+    reference(T* ptr) : ptr_(ptr) {}
+
+    friend bool operator<(reference a, reference b) { return *a.ptr_ < *b.ptr_; }
+    friend bool operator<(reference a, value_type const& b) { return *a.ptr_ < b; }
+    friend bool operator<(value_type const& a, reference b) { return a < *b.ptr_; }
+
+    operator T&() const;
+  };
+
+  Iterator& operator++() {
+    ptr_++;
+    return *this;
+  }
+
+  Iterator operator++(int) {
+    Iterator tmp = *this;
+    ptr_++;
+    return tmp;
+  }
+
+  friend bool operator==(Iterator const& a, Iterator const& b) { return a.ptr_ == b.ptr_; }
+  friend bool operator!=(Iterator const& a, Iterator const& b) { return !(a == b); }
+
+  reference operator*() const { return reference(ptr_); }
+
+  explicit Iterator(T* ptr) : ptr_(ptr) {}
+  Iterator()                = default;
+  Iterator(Iterator const&) = default;
+  Iterator(Iterator&&)      = default;
+
+  Iterator& operator=(Iterator const&) = default;
+  Iterator& operator=(Iterator&&)      = default;
+
+private:
+  T* ptr_;
+};
+
+int main() {
+  int array[5] = {1, 2, 3, 4, 5};
+  Iterator<int> first(array);
+  Iterator<int> middle(array + 3);
+  Iterator<int> last(array + 5);
+  (void)std::binary_search(first, last, 3);
+  (void)std::equal_range(first, last, 3);
+  (void)std::includes(first, last, first, last);
+  (void)std::is_sorted_until(first, last);
+  (void)std::is_sorted(first, last);
+  (void)std::lexicographical_compare(first, last, first, last);
+  (void)std::lower_bound(first, last, 3);
+  (void)std::max_element(first, last);
+  (void)std::min_element(first, last);
+  (void)std::minmax_element(first, last);
+  (void)std::upper_bound(first, last, 3);
+}
diff --git a/libcxx/test/std/containers/sequences/array/compare.verify.cpp b/libcxx/test/std/containers/sequences/array/compare.verify.cpp
--- a/libcxx/test/std/containers/sequences/array/compare.verify.cpp
+++ b/libcxx/test/std/containers/sequences/array/compare.verify.cpp
@@ -28,6 +28,10 @@
 template <int>
 struct NoCompare {};
 
+#if TEST_STD_VER >= 14 && TEST_STD_VER <= 17
+// expected-error@*:* 3 {{no matching function for call to object of type 'std::__less<void, void>'}}
+#endif
+
 int main(int, char**) {
   {
     typedef NoCompare<0> T;
diff --git a/libcxx/utils/data/ignore_format.txt b/libcxx/utils/data/ignore_format.txt
--- a/libcxx/utils/data/ignore_format.txt
+++ b/libcxx/utils/data/ignore_format.txt
@@ -37,7 +37,6 @@
 libcxx/benchmarks/vector_operations.bench.cpp
 libcxx/include/__algorithm/binary_search.h
 libcxx/include/__algorithm/clamp.h
-libcxx/include/__algorithm/comp.h
 libcxx/include/__algorithm/comp_ref_type.h
 libcxx/include/__algorithm/copy_backward.h
 libcxx/include/__algorithm/copy_if.h
@@ -208,7 +207,6 @@
 libcxx/include/__algorithm/uniform_random_bit_generator_adaptor.h
 libcxx/include/__algorithm/unwrap_iter.h
 libcxx/include/__algorithm/unwrap_range.h
-libcxx/include/__algorithm/upper_bound.h
 libcxx/include/any
 libcxx/include/array
 libcxx/include/__atomic/atomic_base.h