diff --git a/doc/mp11/function.adoc b/doc/mp11/function.adoc
index 75c004a..3fa5fc7 100644
--- a/doc/mp11/function.adoc
+++ b/doc/mp11/function.adoc
@@ -100,6 +100,28 @@ using R4 = mp_any<void, mp_true>;      // compile-time error
 
 `mp_same<T...>` is `mp_true` if all the types in `T...` are the same type, `mp_false` otherwise. `mp_same<>` is `mp_true`.
 
+## mp_similar<T...>
+
+    template<class... T> using mp_similar = /*...*/;
+
+`mp_similar<T...>` is `mp_true` if all the types in `T...` are the same type, or instantiations of the same class template
+whose parameters are all types, `mp_false` otherwise. `mp_similar<>` is `mp_true`.
+
+.mp_similar
+```
+using R1 = mp_similar<void>;                        // mp_true
+using R2 = mp_similar<void, void>;                  // mp_true
+using R3 = mp_similar<void, void, void>;            // mp_true
+using R4 = mp_similar<void, void, float>;           // mp_false
+
+template<class T> struct X;
+template<class... T> struct Y;
+
+using R5 = mp_similar<X<int>, X<void>, X<float>>;   // mp_true
+using R6 = mp_similar<Y<>, Y<void>, Y<void, void>>; // mp_true
+using R7 = mp_similar<X<void>, Y<void>>;            // mp_false
+```
+
 ## mp_plus<T...>
 
     template<class... T> using mp_plus = /*...*/;
diff --git a/include/boost/mp11/function.hpp b/include/boost/mp11/function.hpp
index d0fbb25..005bc58 100644
--- a/include/boost/mp11/function.hpp
+++ b/include/boost/mp11/function.hpp
@@ -1,12 +1,12 @@
 #ifndef BOOST_MP11_FUNCTION_HPP_INCLUDED
 #define BOOST_MP11_FUNCTION_HPP_INCLUDED
 
-//  Copyright 2015-2017 Peter Dimov.
+// Copyright 2015-2019 Peter Dimov.
 //
-//  Distributed under the Boost Software License, Version 1.0.
+// Distributed under the Boost Software License, Version 1.0.
 //
-//  See accompanying file LICENSE_1_0.txt or copy at
-//  http://www.boost.org/LICENSE_1_0.txt
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
 
 #include <boost/mp11/integral.hpp>
 #include <boost/mp11/utility.hpp>
@@ -155,6 +155,46 @@ template<class T1, class... T> struct mp_same_impl<T1, T...>
 
 template<class... T> using mp_same = typename detail::mp_same_impl<T...>::type;
 
+// mp_similar<T...>
+namespace detail
+{
+
+template<class... T> struct mp_similar_impl;
+
+template<> struct mp_similar_impl<>
+{
+    using type = mp_true;
+};
+
+template<class T> struct mp_similar_impl<T>
+{
+    using type = mp_true;
+};
+
+template<class T> struct mp_similar_impl<T, T>
+{
+    using type = mp_true;
+};
+
+template<class T1, class T2> struct mp_similar_impl<T1, T2>
+{
+    using type = mp_false;
+};
+
+template<template<class...> class L, class... T1, class... T2> struct mp_similar_impl<L<T1...>, L<T2...>>
+{
+    using type = mp_true;
+};
+
+template<class T1, class T2, class T3, class... T> struct mp_similar_impl<T1, T2, T3, T...>
+{
+    using type = mp_all< typename mp_similar_impl<T1, T2>::type, typename mp_similar_impl<T1, T3>::type, typename mp_similar_impl<T1, T>::type... >;
+};
+
+} // namespace detail
+
+template<class... T> using mp_similar = typename detail::mp_similar_impl<T...>::type;
+
 // mp_less<T1, T2>
 template<class T1, class T2> using mp_less = mp_bool<(T1::value < 0 && T2::value >= 0) || ((T1::value < T2::value) && !(T1::value >= 0 && T2::value < 0))>;
 
diff --git a/test/Jamfile b/test/Jamfile
index 5c9d59a..735e07c 100644
--- a/test/Jamfile
+++ b/test/Jamfile
@@ -143,6 +143,7 @@ run mp_plus.cpp ;
 run mp_less.cpp ;
 run mp_min.cpp ;
 run mp_max.cpp ;
+run mp_similar.cpp ;
 
 # map
 run mp_map_find.cpp ;
diff --git a/test/mp_similar.cpp b/test/mp_similar.cpp
new file mode 100644
index 0000000..5fb538f
--- /dev/null
+++ b/test/mp_similar.cpp
@@ -0,0 +1,45 @@
+
+// Copyright 2019 Peter Dimov.
+//
+// Distributed under the Boost Software License, Version 1.0.
+//
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+
+
+#include <boost/mp11/function.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+
+template<class> class X;
+template<class...> class Y;
+
+int main()
+{
+    using boost::mp11::mp_similar;
+    using boost::mp11::mp_true;
+    using boost::mp11::mp_false;
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<void>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<void, void>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<void, void, void>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<void, void, void, void>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<void, void, void, void, void>, mp_true>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<void, int>, mp_false>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<void, void, int>, mp_false>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<void, void, void, int>, mp_false>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<void, void, void, void, int>, mp_false>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<X<void>>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<X<void>, X<int>>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<X<void>, X<int>, X<float>>, mp_true>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<Y<>>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<Y<>, Y<void>>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<Y<>, Y<void>, Y<void, void>>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_similar<Y<>, Y<void>, Y<void, void>, Y<void, void, void>>, mp_true>));
+
+    return boost::report_errors();
+}