diff --git a/libcxx/docs/ReleaseNotes.rst b/libcxx/docs/ReleaseNotes.rst
--- a/libcxx/docs/ReleaseNotes.rst
+++ b/libcxx/docs/ReleaseNotes.rst
@@ -41,6 +41,8 @@
 Improvements and New Features
 -----------------------------
 
+* Implemented ``operator<=>`` for ``std::unique_ptr``
+
 Deprecations and Removals
 -------------------------
 
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
@@ -25,7 +25,7 @@
 "| `[variant.relops] <https://wg21.link/variant.relops>`_
 | `[variant.monostate.relops] <https://wg21.link/variant.monostate.relops>`_","| monostate
 | variant",None,Kent Ross,|In Progress|
-| `[unique.ptr.special] <https://wg21.link/unique.ptr.special>`_,| unique_ptr,[comparisons.three.way],Unassigned,|Not Started|
+| `[unique.ptr.special] <https://wg21.link/unique.ptr.special>`_,| unique_ptr,[comparisons.three.way],Adrian Vogelsgesang,|Complete|
 | `[util.smartptr.shared.cmp] <https://wg21.link/util.smartptr.shared.cmp>`_,| shared_ptr,[comparisons.three.way],Unassigned,|Not Started|
 | `[type.index.members] <https://wg21.link/type.index.members>`_,| type_index,None,Unassigned,|Not Started|
 | `[charconv.syn] <https://wg21.link/charconv.syn>`_,| to_chars_result,None,Mark de Wever,|Complete|
diff --git a/libcxx/include/__memory/unique_ptr.h b/libcxx/include/__memory/unique_ptr.h
--- a/libcxx/include/__memory/unique_ptr.h
+++ b/libcxx/include/__memory/unique_ptr.h
@@ -10,6 +10,9 @@
 #ifndef _LIBCPP___MEMORY_UNIQUE_PTR_H
 #define _LIBCPP___MEMORY_UNIQUE_PTR_H
 
+#include <__compare/compare_three_way.h>
+#include <__compare/compare_three_way_result.h>
+#include <__compare/three_way_comparable.h>
 #include <__config>
 #include <__functional/hash.h>
 #include <__functional/operations.h>
@@ -557,10 +560,12 @@
 bool
 operator==(const unique_ptr<_T1, _D1>& __x, const unique_ptr<_T2, _D2>& __y) {return __x.get() == __y.get();}
 
+#if _LIBCPP_STD_VER <= 17
 template <class _T1, class _D1, class _T2, class _D2>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
 operator!=(const unique_ptr<_T1, _D1>& __x, const unique_ptr<_T2, _D2>& __y) {return !(__x == __y);}
+#endif
 
 template <class _T1, class _D1, class _T2, class _D2>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -588,6 +593,18 @@
 bool
 operator>=(const unique_ptr<_T1, _D1>& __x, const unique_ptr<_T2, _D2>& __y) {return !(__x < __y);}
 
+
+#if _LIBCPP_STD_VER > 17
+template <class _T1, class _D1, class _T2, class _D2>
+requires three_way_comparable_with<typename unique_ptr<_T1, _D1>::pointer,
+                                   typename unique_ptr<_T2, _D2>::pointer>
+compare_three_way_result_t<typename unique_ptr<_T1, _D1>::pointer,
+                           typename unique_ptr<_T2, _D2>::pointer>
+operator<=>(const unique_ptr<_T1, _D1>& __x, const unique_ptr<_T2, _D2>& __y) {
+   return compare_three_way()(__x.get(), __y.get());
+}
+#endif
+
 template <class _T1, class _D1>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
@@ -596,6 +613,7 @@
     return !__x;
 }
 
+#if _LIBCPP_STD_VER <= 17
 template <class _T1, class _D1>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
@@ -619,6 +637,7 @@
 {
     return static_cast<bool>(__x);
 }
+#endif // _LIBCPP_STD_VER <= 17
 
 template <class _T1, class _D1>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -686,6 +705,15 @@
     return !(nullptr < __x);
 }
 
+#if _LIBCPP_STD_VER > 17
+template <class _T1, class _D1>
+requires three_way_comparable<typename unique_ptr<_T1, _D1>::pointer>
+compare_three_way_result_t<typename unique_ptr<_T1, _D1>::pointer>
+operator<=>(const unique_ptr<_T1, _D1>& __x, nullptr_t) {
+   return compare_three_way()(__x.get(), static_cast<typename unique_ptr<_T1, _D1>::pointer>(nullptr));
+}
+#endif
+
 #if _LIBCPP_STD_VER > 11
 
 template<class _Tp>
diff --git a/libcxx/include/memory b/libcxx/include/memory
--- a/libcxx/include/memory
+++ b/libcxx/include/memory
@@ -505,7 +505,7 @@
 template <class T1, class D1, class T2, class D2>
     bool operator==(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
 template <class T1, class D1, class T2, class D2>
-    bool operator!=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
+    bool operator!=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);    // removed in C++20
 template <class T1, class D1, class T2, class D2>
     bool operator<(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
 template <class T1, class D1, class T2, class D2>
@@ -514,15 +514,21 @@
     bool operator>(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
 template <class T1, class D1, class T2, class D2>
     bool operator>=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
+template<class T1, class D1, class T2, class D2>
+  requires three_way_comparable_with<typename unique_ptr<T1, D1>::pointer,
+                                     typename unique_ptr<T2, D2>::pointer>
+  compare_three_way_result_t<typename unique_ptr<T1, D1>::pointer,
+                             typename unique_ptr<T2, D2>::pointer>
+    operator<=>(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);      // C++20
 
 template <class T, class D>
     bool operator==(const unique_ptr<T, D>& x, nullptr_t) noexcept;
 template <class T, class D>
-    bool operator==(nullptr_t, const unique_ptr<T, D>& y) noexcept;
+    bool operator==(nullptr_t, const unique_ptr<T, D>& y) noexcept;     // removed in C++20
 template <class T, class D>
-    bool operator!=(const unique_ptr<T, D>& x, nullptr_t) noexcept;
+    bool operator!=(const unique_ptr<T, D>& x, nullptr_t) noexcept;     // removed in C++20
 template <class T, class D>
-    bool operator!=(nullptr_t, const unique_ptr<T, D>& y) noexcept;
+    bool operator!=(nullptr_t, const unique_ptr<T, D>& y) noexcept;     // removed in C++20
 
 template <class T, class D>
     bool operator<(const unique_ptr<T, D>& x, nullptr_t);
@@ -540,6 +546,10 @@
     bool operator>=(const unique_ptr<T, D>& x, nullptr_t);
 template <class T, class D>
     bool operator>=(nullptr_t, const unique_ptr<T, D>& y);
+template<class T, class D>
+  requires three_way_comparable<typename unique_ptr<T, D>::pointer>
+  compare_three_way_result_t<typename unique_ptr<T, D>::pointer>
+    operator<=>(const unique_ptr<T, D>& x, nullptr_t);                          // C++20
 
 class bad_weak_ptr
     : public std::exception
diff --git a/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.special/cmp_nullptr.pass.cpp b/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.special/cmp_nullptr.pass.cpp
--- a/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.special/cmp_nullptr.pass.cpp
+++ b/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.special/cmp_nullptr.pass.cpp
@@ -34,6 +34,10 @@
 //     bool operator>=(const unique_ptr<T, D>& x, nullptr_t) noexcept;
 // template <class T, class D>
 //     bool operator>=(nullptr_t, const unique_ptr<T, D>& y) noexcept;
+// template<class T, class D>
+//   requires three_­way_­comparable<typename unique_ptr<T, D>::pointer>
+//   constexpr compare_three_way_result_t<typename unique_ptr<T, D>::pointer>
+//     operator<=>(const unique_ptr<T, D>& x, nullptr_t);                            // C++20
 
 #include <memory>
 #include <cassert>
@@ -55,6 +59,10 @@
     assert(!(nullptr > p1));
     assert( (p1 >= nullptr));
     assert(!(nullptr >= p1));
+#if TEST_STD_VER > 17
+    assert((nullptr <=> p1) == std::strong_ordering::less);
+    assert((p1 <=> nullptr) == std::strong_ordering::greater);
+#endif
 
     const std::unique_ptr<int> p2;
     assert( (p2 == nullptr));
@@ -67,6 +75,9 @@
     assert(!(nullptr > p2));
     assert( (p2 >= nullptr));
     assert( (nullptr >= p2));
+#if TEST_STD_VER > 17
+    assert((nullptr <=> p2) == std::strong_ordering::equivalent);
+#endif
 
-  return 0;
+    return 0;
 }
diff --git a/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.special/rel.pass.cpp b/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.special/rel.pass.cpp
--- a/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.special/rel.pass.cpp
+++ b/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.special/rel.pass.cpp
@@ -26,6 +26,13 @@
 //   bool
 //   operator>=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
 
+// template<class T1, class D1, class T2, class D2>
+//   requires three_way_comparable_with<typename unique_ptr<T1, D1>::pointer,
+//                                      typename unique_ptr<T2, D2>::pointer>
+//   compare_three_way_result_t<typename unique_ptr<T1, D1>::pointer,
+//                              typename unique_ptr<T2, D2>::pointer>
+//     operator<=>(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
+
 #include <memory>
 #include <cassert>
 
@@ -53,6 +60,10 @@
 
 int B::count = 0;
 
+#if TEST_STD_VER > 17
+static std::strong_ordering reverse(std::strong_ordering v) { return 0 <=> v; }
+#endif
+
 int main(int, char**)
 {
     {
@@ -61,6 +72,10 @@
     assert((p1 < p2) == !(p1 > p2));
     assert((p1 < p2) == (p1 <= p2));
     assert((p1 < p2) == !(p1 >= p2));
+#if TEST_STD_VER > 17
+    assert((p1 <=> p1) == std::strong_ordering::equivalent);
+    assert((p1 <=> p2) == reverse(p2 <=> p1));
+#endif
     }
     {
     const std::unique_ptr<A, Deleter<A> > p1(new A);
@@ -68,6 +83,9 @@
     assert((p1 < p2) == !(p1 > p2));
     assert((p1 < p2) == (p1 <= p2));
     assert((p1 < p2) == !(p1 >= p2));
+#if TEST_STD_VER > 17
+    assert((p1 <=> p2) == reverse(p2 <=> p1));
+#endif
     }
     {
     const std::unique_ptr<A[], Deleter<A[]> > p1(new A[3]);
@@ -75,6 +93,9 @@
     assert((p1 < p2) == !(p1 > p2));
     assert((p1 < p2) == (p1 <= p2));
     assert((p1 < p2) == !(p1 >= p2));
+#if TEST_STD_VER > 17
+    assert((p1 <=> p2) == reverse(p2 <=> p1));
+#endif
     }
     {
     const std::unique_ptr<A[], Deleter<A[]> > p1(new A[3]);
@@ -82,6 +103,9 @@
     assert((p1 < p2) == !(p1 > p2));
     assert((p1 < p2) == (p1 <= p2));
     assert((p1 < p2) == !(p1 >= p2));
+#if TEST_STD_VER > 17
+    assert((p1 <=> p2) == reverse(p2 <=> p1));
+#endif
     }
     {
     const std::unique_ptr<A, Deleter<A> > p1;
@@ -89,6 +113,9 @@
     assert((p1 < p2) == (p1 > p2));
     assert((p1 < p2) == !(p1 <= p2));
     assert((p1 < p2) == !(p1 >= p2));
+#if TEST_STD_VER > 17
+    assert((p1 <=> p2) == reverse(p2 <=> p1));
+#endif
     }
     {
     const std::unique_ptr<A, Deleter<A> > p1;
@@ -96,6 +123,9 @@
     assert((p1 < p2) == (p1 > p2));
     assert((p1 < p2) == !(p1 <= p2));
     assert((p1 < p2) == !(p1 >= p2));
+#if TEST_STD_VER > 17
+    assert((p1 <=> p2) == reverse(p2 <=> p1));
+#endif
     }
 
   return 0;