diff --git a/include/etl/unordered_map.h b/include/etl/unordered_map.h
index a4488101f..54d0bafaa 100644
--- a/include/etl/unordered_map.h
+++ b/include/etl/unordered_map.h
@@ -1681,6 +1681,25 @@ namespace etl
     }
 #endif
 
+    //*************************************************************************
+    /// Check if the unordered_map contains the key.
+    //*************************************************************************
+    bool contains(const_key_reference key) const
+    {
+      return find(key) != end();
+    }
+
+#if ETL_USING_CPP11
+    //*************************************************************************
+    /// Check if the unordered_map contains the key.
+    //*************************************************************************
+    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
+    bool contains(const K& key) const
+    {
+      return find(key) != end();
+    }
+#endif
+
   protected:
 
     //*********************************************************************
diff --git a/include/etl/unordered_multimap.h b/include/etl/unordered_multimap.h
index 122868b0e..3db0d1f5c 100644
--- a/include/etl/unordered_multimap.h
+++ b/include/etl/unordered_multimap.h
@@ -1442,6 +1442,25 @@ namespace etl
     }
 #endif
 
+    //*************************************************************************
+    /// Check if the unordered_multimap contains the key.
+    //*************************************************************************
+    bool contains(const_key_reference key) const
+    {
+      return find(key) != end();
+    }
+
+#if ETL_USING_CPP11
+    //*************************************************************************
+    /// Check if the unordered_map contains the key.
+    //*************************************************************************
+    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
+    bool contains(const K& key) const
+    {
+      return find(key) != end();
+    }
+#endif
+
   protected:
 
     //*********************************************************************
diff --git a/include/etl/unordered_multiset.h b/include/etl/unordered_multiset.h
index f2b28a585..e0cf15909 100644
--- a/include/etl/unordered_multiset.h
+++ b/include/etl/unordered_multiset.h
@@ -1493,6 +1493,25 @@ namespace etl
     }
 #endif
 
+    //*************************************************************************
+    /// Check if the unordered_multiset contains the key.
+    //*************************************************************************
+    bool contains(key_parameter_t key) const
+    {
+      return find(key) != end();
+    }
+
+#if ETL_USING_CPP11
+    //*************************************************************************
+    /// Check if the unordered_map contains the key.
+    //*************************************************************************
+    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
+    bool contains(const K& key) const
+    {
+      return find(key) != end();
+    }
+#endif
+
   protected:
 
     //*********************************************************************
diff --git a/include/etl/unordered_set.h b/include/etl/unordered_set.h
index b08bd7552..795eabfd6 100644
--- a/include/etl/unordered_set.h
+++ b/include/etl/unordered_set.h
@@ -1502,6 +1502,25 @@ namespace etl
     }
 #endif
 
+    //*************************************************************************
+    /// Check if the unordered_set contains the key.
+    //*************************************************************************
+    bool contains(key_parameter_t key) const
+    {
+      return find(key) != end();
+    }
+
+#if ETL_USING_CPP11
+    //*************************************************************************
+    /// Check if the unordered_map contains the key.
+    //*************************************************************************
+    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
+    bool contains(const K& key) const
+    {
+      return find(key) != end();
+    }
+#endif
+
   protected:
 
     //*********************************************************************
diff --git a/test/test_unordered_map.cpp b/test/test_unordered_map.cpp
index 382653372..c38fb0dd9 100644
--- a/test/test_unordered_map.cpp
+++ b/test/test_unordered_map.cpp
@@ -1409,5 +1409,27 @@ namespace
       CHECK_TRUE(map1 == map2a);
       CHECK_FALSE(map1 == map2b);
     }
+
+    //*************************************************************************
+    TEST(test_contains)
+    {
+      DataNDC data(initial_data.begin(), initial_data.end());
+
+      const char* not_inserted  = "ZZ";
+
+      CHECK_TRUE(data.contains(K0));
+      CHECK_FALSE(data.contains(std::string(not_inserted)));
+    }
+
+    //*************************************************************************
+    TEST(test_contains_with_transparent_comparator)
+    {
+      DataNDCTransparent data(initial_data.begin(), initial_data.end());
+
+      const char* not_inserted  = "ZZ";
+
+      CHECK_TRUE(data.contains("FF"));
+      CHECK_FALSE(data.contains(not_inserted));
+    }
   };
 }
diff --git a/test/test_unordered_multimap.cpp b/test/test_unordered_multimap.cpp
index a5fccb25c..716636e0e 100644
--- a/test/test_unordered_multimap.cpp
+++ b/test/test_unordered_multimap.cpp
@@ -1226,5 +1226,27 @@ namespace
       CHECK_TRUE(map1 == map2a);
       CHECK_FALSE(map1 == map2b);
     }
+
+    //*************************************************************************
+    TEST(test_contains)
+    {
+      DataNDC data(initial_data.begin(), initial_data.end());
+
+      const char* not_inserted  = "ZZ";
+
+      CHECK_TRUE(data.contains(K0));
+      CHECK_FALSE(data.contains(not_inserted));
+    }
+
+    //*************************************************************************
+    TEST(test_contains_with_transparent_comparator)
+    {
+      DataNDCTransparent data(initial_data.begin(), initial_data.end());
+
+      const char* not_inserted  = "ZZ";
+
+      CHECK_TRUE(data.contains("FF"));
+      CHECK_FALSE(data.contains(not_inserted));
+    }
   };
 }
diff --git a/test/test_unordered_multiset.cpp b/test/test_unordered_multiset.cpp
index 3e58dd6c6..27bfe310e 100644
--- a/test/test_unordered_multiset.cpp
+++ b/test/test_unordered_multiset.cpp
@@ -1079,5 +1079,29 @@ namespace
       CHECK_TRUE(set1 == set2a);
       CHECK_FALSE(set1 == set2b);
     }
+
+    //*************************************************************************
+    TEST(test_contains)
+    {
+      DataNDC data(initial_data.begin(), initial_data.end());
+
+      NDC not_inserted  = NDC("ZZ");
+
+      CHECK_TRUE(data.contains(N0));
+      CHECK_FALSE(data.contains(not_inserted));
+    }
+
+    //*************************************************************************
+    TEST(test_contains_with_transparent_comparator)
+    {
+      std::array<const char*, 8> initial = { "AA", "BB", "CC", "DD", "EE", "FF", "GG", "HH" };
+
+      DataTransparent data(initial.begin(), initial.end());
+
+      const char* not_inserted  = "ZZ";
+
+      CHECK_TRUE(data.contains("FF"));
+      CHECK_FALSE(data.contains(not_inserted));
+    }
   };
 }
diff --git a/test/test_unordered_set.cpp b/test/test_unordered_set.cpp
index 33eecb889..189f97615 100644
--- a/test/test_unordered_set.cpp
+++ b/test/test_unordered_set.cpp
@@ -1044,5 +1044,29 @@ namespace
       CHECK_TRUE(set1 == set2a);
       CHECK_FALSE(set1 == set2b);
     }
+
+    //*************************************************************************
+    TEST(test_contains)
+    {
+      DataNDC data(initial_data.begin(), initial_data.end());
+
+      NDC not_inserted  = NDC("ZZ");
+
+      CHECK_TRUE(data.contains(N0));
+      CHECK_FALSE(data.contains(not_inserted));
+    }
+
+    //*************************************************************************
+    TEST(test_contains_with_transparent_comparator)
+    {
+      std::array<const char*, 8> initial = { "AA", "BB", "CC", "DD", "EE", "FF", "GG", "HH" };
+
+      DataTransparent data(initial.begin(), initial.end());
+
+      const char* not_inserted  = "ZZ";
+
+      CHECK_TRUE(data.contains("FF"));
+      CHECK_FALSE(data.contains(not_inserted));
+    }
   };
 }