diff --git a/libcxx/docs/Status/SpaceshipProjects.csv b/libcxx/docs/Status/SpaceshipProjects.csv
--- a/libcxx/docs/Status/SpaceshipProjects.csv
+++ b/libcxx/docs/Status/SpaceshipProjects.csv
@@ -39,7 +39,7 @@
 | `[deque.syn] <https://wg21.link/deque.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),| deque,[expos.only.func],Unassigned,|Not Started|
 | `[forward.list.syn] <https://wg21.link/forward.list.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),| forward_list,[expos.only.func],Unassigned,|Not Started|
 | `[list.syn] <https://wg21.link/list.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),| `list <https://reviews.llvm.org/D132312>`_,[expos.only.func],Adrian Vogelsgesang,|Complete|
-| `[vector.syn] <https://wg21.link/vector.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),| `vector <https://reviews.llvm.org/D132268>`_,[expos.only.func],Adrian Vogelsgesang,|In Progress|
+| `[vector.syn] <https://wg21.link/vector.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),| `vector <https://reviews.llvm.org/D132268>`_,[expos.only.func],Adrian Vogelsgesang,|Complete|
 | `[associative.map.syn] <https://wg21.link/associative.map.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),"| map
 | multimap",[expos.only.func],Unassigned,|Not Started|
 | `[associative.set.syn] <https://wg21.link/associative.set.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),"| multiset
diff --git a/libcxx/include/vector b/libcxx/include/vector
--- a/libcxx/include/vector
+++ b/libcxx/include/vector
@@ -249,12 +249,14 @@
 
 template <class Allocator> struct hash<std::vector<bool, Allocator>>;
 
-template <class T, class Allocator> bool operator==(const vector<T,Allocator>& x, const vector<T,Allocator>& y);
-template <class T, class Allocator> bool operator< (const vector<T,Allocator>& x, const vector<T,Allocator>& y);
-template <class T, class Allocator> bool operator!=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);
-template <class T, class Allocator> bool operator> (const vector<T,Allocator>& x, const vector<T,Allocator>& y);
-template <class T, class Allocator> bool operator>=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);
-template <class T, class Allocator> bool operator<=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);
+template <class T, class Allocator> bool operator==(const vector<T,Allocator>& x, const vector<T,Allocator>& y);   // constexpr since C++20
+template <class T, class Allocator> bool operator!=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);   // removed in C++20
+template <class T, class Allocator> bool operator< (const vector<T,Allocator>& x, const vector<T,Allocator>& y);   // removed in C++20
+template <class T, class Allocator> bool operator> (const vector<T,Allocator>& x, const vector<T,Allocator>& y);   // removed in C++20
+template <class T, class Allocator> bool operator>=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);   // removed in C++20
+template <class T, class Allocator> bool operator<=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);   // removed in C++20
+template <class T, class Allocator> constexpr
+    synth-three-way-result<T> operator<=>(const vector<T, Allocator>& x, const vector<T, Allocator>& y);           // since C++20
 
 template <class T, class Allocator>
 void swap(vector<T,Allocator>& x, vector<T,Allocator>& y)
@@ -262,10 +264,10 @@
 
 template <class T, class Allocator, class U>
 typename vector<T, Allocator>::size_type
-erase(vector<T, Allocator>& c, const U& value);       // C++20
+erase(vector<T, Allocator>& c, const U& value);       // since C++20
 template <class T, class Allocator, class Predicate>
 typename vector<T, Allocator>::size_type
-erase_if(vector<T, Allocator>& c, Predicate pred);    // C++20
+erase_if(vector<T, Allocator>& c, Predicate pred);    // since C++20
 
 
 template<class T>
@@ -282,6 +284,7 @@
 #include <__algorithm/equal.h>
 #include <__algorithm/fill_n.h>
 #include <__algorithm/lexicographical_compare.h>
+#include <__algorithm/lexicographical_compare_three_way.h>
 #include <__algorithm/remove.h>
 #include <__algorithm/remove_if.h>
 #include <__algorithm/rotate.h>
@@ -3257,8 +3260,9 @@
     return __sz == __y.size() && std::equal(__x.begin(), __x.end(), __y.begin());
 }
 
+#if _LIBCPP_STD_VER <= 17
+
 template <class _Tp, class _Allocator>
-_LIBCPP_CONSTEXPR_SINCE_CXX20
 inline _LIBCPP_HIDE_FROM_ABI
 bool
 operator!=(const vector<_Tp, _Allocator>& __x, const vector<_Tp, _Allocator>& __y)
@@ -3267,7 +3271,6 @@
 }
 
 template <class _Tp, class _Allocator>
-_LIBCPP_CONSTEXPR_SINCE_CXX20
 inline _LIBCPP_HIDE_FROM_ABI
 bool
 operator< (const vector<_Tp, _Allocator>& __x, const vector<_Tp, _Allocator>& __y)
@@ -3276,7 +3279,6 @@
 }
 
 template <class _Tp, class _Allocator>
-_LIBCPP_CONSTEXPR_SINCE_CXX20
 inline _LIBCPP_HIDE_FROM_ABI
 bool
 operator> (const vector<_Tp, _Allocator>& __x, const vector<_Tp, _Allocator>& __y)
@@ -3285,7 +3287,6 @@
 }
 
 template <class _Tp, class _Allocator>
-_LIBCPP_CONSTEXPR_SINCE_CXX20
 inline _LIBCPP_HIDE_FROM_ABI
 bool
 operator>=(const vector<_Tp, _Allocator>& __x, const vector<_Tp, _Allocator>& __y)
@@ -3294,7 +3295,6 @@
 }
 
 template <class _Tp, class _Allocator>
-_LIBCPP_CONSTEXPR_SINCE_CXX20
 inline _LIBCPP_HIDE_FROM_ABI
 bool
 operator<=(const vector<_Tp, _Allocator>& __x, const vector<_Tp, _Allocator>& __y)
@@ -3302,6 +3302,18 @@
     return !(__y < __x);
 }
 
+#else // _LIBCPP_STD_VER <= 17
+
+template<class _Tp, class _Allocator>
+inline _LIBCPP_HIDE_FROM_ABI
+constexpr __synth_three_way_result<_Tp>
+operator<=>(const vector<_Tp, _Allocator>& __x, const vector<_Tp, _Allocator>& __y)
+{
+    return lexicographical_compare_three_way(__x.begin(), __x.end(), __y.begin(), __y.end(), __synth_three_way);
+}
+
+#endif // _LIBCPP_STD_VER <= 17
+
 template <class _Tp, class _Allocator>
 _LIBCPP_CONSTEXPR_SINCE_CXX20
 inline _LIBCPP_HIDE_FROM_ABI
diff --git a/libcxx/test/std/containers/sequences/vector/compare.three_way.pass.cpp b/libcxx/test/std/containers/sequences/vector/compare.three_way.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/containers/sequences/vector/compare.three_way.pass.cpp
@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <vector>
+
+// template <class T, class Allocator> constexpr
+//   synth-three-way-result<T>
+//     operator<=>(const vector<T, Allocator>& x, const vector<T, Allocator>& y);
+
+#include <vector>
+#include <cassert>
+
+#include "test_container_comparisons.h"
+
+int main(int, char**) {
+  assert(test_ordered_container_spaceship<std::vector>());
+  static_assert(test_ordered_container_spaceship<std::vector>());
+  return 0;
+}