diff --git a/lib/hash_map.c b/lib/hash_map.c
index cab21e1..67a781e 100644
--- a/lib/hash_map.c
+++ b/lib/hash_map.c
@@ -217,3 +217,12 @@ string_t *hash_map_get_keys(struct hash_map *hash_map) {
   }
   return keys;
 }
+
+void hash_map_free(struct hash_map *hash_map) {
+  for (size_t index = 0; index < hash_map->capacity; index++) {
+    if (hash_map->items[index] != NULL) {
+      linked_list_free(hash_map->items[index]);
+    }
+  }
+  free(hash_map);
+}
diff --git a/lib/hash_map.h b/lib/hash_map.h
index 8981601..71bac7e 100644
--- a/lib/hash_map.h
+++ b/lib/hash_map.h
@@ -89,4 +89,10 @@ bool hash_map_contains_key(struct hash_map *hash_map, string_t key);
  */
 string_t *hash_map_get_keys(struct hash_map *hash_map);
 
+/**
+ * @brief Frees the hash map.
+ * @since v2.1.0
+ */
+void hash_map_free(struct hash_map *hash_map);
+
 #endif
diff --git a/lib/linked_list.c b/lib/linked_list.c
index e3298d7..5fd98cc 100644
--- a/lib/linked_list.c
+++ b/lib/linked_list.c
@@ -92,5 +92,6 @@ void linked_list_free(struct linked_list *list) {
     node_current = node_current->next;
     free(node_to_remove);
   }
+  list->head = NULL;
   free(list);
 }
diff --git a/lib/string.c b/lib/string.c
index 16fba0a..b076e38 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -285,6 +285,7 @@ bool string_get_has_unique_characters(const string_t string_value) {
       hash_map_add(characters_already_seen, key, (void*)true);
     }
   }
+  hash_map_free(characters_already_seen);
   return has_unique;
 }
 
diff --git a/test/hash_map_test.c b/test/hash_map_test.c
index 25411e0..4074127 100644
--- a/test/hash_map_test.c
+++ b/test/hash_map_test.c
@@ -24,4 +24,5 @@ void hash_map_test() {
   hash_map_remove(hash_map, "key5");
   assert(hash_map->length == 5);
   assert(!hash_map_contains_key(hash_map, "key5"));
+  hash_map_free(hash_map);
 }