diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 4d555bd33e..16f9db95fc 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   PostgreSQL and SQLite string columns no longer have a default limit of 255.
+
+    Fixes #13435, #9153.
+
+    *Vladimir Sazhin*, *Toms Mikoss*, *Yves Senn*
+
 *   Make possible to have an association called `records`.
 
     Fixes #11645.
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 9fe8e0497e..3510e4f3b0 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -209,7 +209,7 @@ module ActiveRecord
 
       NATIVE_DATABASE_TYPES = {
         primary_key: "serial primary key",
-        string:      { name: "character varying", limit: 255 },
+        string:      { name: "character varying" },
         text:        { name: "text" },
         integer:     { name: "integer" },
         float:       { name: "float" },
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 6e6a51dab8..cd1f7a16c6 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -63,7 +63,7 @@ module ActiveRecord
 
       NATIVE_DATABASE_TYPES = {
         primary_key:  'INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL',
-        string:       { name: "varchar", limit: 255 },
+        string:       { name: "varchar" },
         text:         { name: "text" },
         integer:      { name: "integer" },
         float:        { name: "float" },
diff --git a/activerecord/test/cases/adapters/postgresql/array_test.rb b/activerecord/test/cases/adapters/postgresql/array_test.rb
index 36ded66998..18dd4a6de8 100644
--- a/activerecord/test/cases/adapters/postgresql/array_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/array_test.rb
@@ -25,7 +25,7 @@ class PostgresqlArrayTest < ActiveRecord::TestCase
 
   def test_column
     assert_equal :string, @column.type
-    assert_equal "character varying(255)", @column.sql_type
+    assert_equal "character varying", @column.sql_type
     assert @column.array
     assert_not @column.text?
     assert_not @column.number?
diff --git a/activerecord/test/cases/migration/column_attributes_test.rb b/activerecord/test/cases/migration/column_attributes_test.rb
index ccf19fb4d0..6a02873cba 100644
--- a/activerecord/test/cases/migration/column_attributes_test.rb
+++ b/activerecord/test/cases/migration/column_attributes_test.rb
@@ -35,6 +35,14 @@ module ActiveRecord
         assert_no_column TestModel, :last_name
       end
 
+      def test_add_column_without_limit
+        # TODO: limit: nil should work with all adapters.
+        skip "MySQL wrongly enforces a limit of 255" if current_adapter?(:MysqlAdapter, :Mysql2Adapter)
+        add_column :test_models, :description, :string, limit: nil
+        TestModel.reset_column_information
+        assert_nil TestModel.columns_hash["description"].limit
+      end
+
       if current_adapter?(:MysqlAdapter, :Mysql2Adapter)
         def test_unabstracted_database_dependent_types
           add_column :test_models, :intelligence_quotient, :tinyint
diff --git a/activerecord/test/cases/reflection_test.rb b/activerecord/test/cases/reflection_test.rb
index d7ad5ed29f..ad77472333 100644
--- a/activerecord/test/cases/reflection_test.rb
+++ b/activerecord/test/cases/reflection_test.rb
@@ -63,7 +63,7 @@ class ReflectionTest < ActiveRecord::TestCase
 
   def test_column_string_type_and_limit
     assert_equal :string, @first.column_for_attribute("title").type
-    assert_equal 255, @first.column_for_attribute("title").limit
+    assert_equal 250, @first.column_for_attribute("title").limit
   end
 
   def test_column_null_not_null
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 5bd3a51a84..d9e1745029 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -677,7 +677,7 @@ ActiveRecord::Schema.define do
   end
 
   create_table :topics, force: true do |t|
-    t.string   :title
+    t.string   :title, limit: 250
     t.string   :author_name
     t.string   :author_email_address
     if mysql_56?