diff --git a/src/include/units/bits/external/type_list.h b/src/include/units/bits/external/type_list.h
index 422bb00f..4126738e 100644
--- a/src/include/units/bits/external/type_list.h
+++ b/src/include/units/bits/external/type_list.h
@@ -73,6 +73,25 @@ namespace units {
   template<TypeList List, typename... Types>
   using type_list_push_back = detail::type_list_push_back_impl<List, Types...>::type;
 
+  // join
+
+  namespace detail {
+
+    template<typename List, typename... Rest>
+    struct type_list_join_impl {
+      using type = List;
+    };
+
+    template<template<typename...> typename List, typename... First, typename... Second, typename... Rest>
+    struct type_list_join_impl<List<First...>, List<Second...>, Rest...> {
+      using type = type_list_join_impl<List<First..., Second...>, Rest...>::type;
+    };
+
+  }
+
+  template<TypeList... Lists>
+  using type_list_join = detail::type_list_join_impl<Lists...>::type;
+
   // split
 
   namespace detail {
diff --git a/test/unit_test/static/type_list_test.cpp b/test/unit_test/static/type_list_test.cpp
index 45221d56..c29f0c54 100644
--- a/test/unit_test/static/type_list_test.cpp
+++ b/test/unit_test/static/type_list_test.cpp
@@ -44,6 +44,15 @@ static_assert(std::is_same_v<type_list_push_back<type_list<>, int>, type_list<in
 static_assert(std::is_same_v<type_list_push_back<type_list<>, int, long, double>, type_list<int, long, double>>);
 static_assert(std::is_same_v<type_list_push_back<type_list<double>, int, long>, type_list<double, int, long>>);
 
+static_assert(std::is_same_v<type_list_join<type_list<>>, type_list<>>);
+static_assert(std::is_same_v<type_list_join<type_list<>, type_list<>>, type_list<>>);
+static_assert(std::is_same_v<type_list_join<type_list<>, type_list<>, type_list<>>, type_list<>>);
+static_assert(std::is_same_v<type_list_join<type_list<int>, type_list<>, type_list<>>, type_list<int>>);
+static_assert(std::is_same_v<type_list_join<type_list<>, type_list<int>, type_list<>>, type_list<int>>);
+static_assert(std::is_same_v<type_list_join<type_list<>, type_list<>, type_list<int>>, type_list<int>>);
+static_assert(std::is_same_v<type_list_join<type_list<int>, type_list<float>, type_list<bool>>, type_list<int, float, bool>>);
+static_assert(std::is_same_v<type_list_join<type_list<int, short>, type_list<float, double>, type_list<bool>>, type_list<int, short, float, double, bool>>);
+
 // type_list_split
 
 static_assert(std::is_same_v<type_list_split<type_list<int>, 0>::first_list, type_list<>>);