diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6859b67..7422775 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
   * Address [#425](https://github.com/seancorfield/honeysql/issues/425) by clarifying that `INTERVAL` as special syntax may be MySQL-specific and PostgreSQL uses difference syntax (because `INTERVAL` is a data type there).
   * Address [#423](https://github.com/seancorfield/honeysql/issues/423) by supporting `DEFAULT` values and `DEFAULT` rows in `VALUES`.
   * Address [#422](https://github.com/seancorfield/honeysql/issues/422) by auto-quoting unusual entity names when `:quoted` (and `:dialect`) are not specified, making HoneySQL more secure by default.
+  * Fix [#421](https://github.com/seancorfield/honeysql/issues/421) by adding `:replace-into` for `:mysql` dialect.
   * Address [#419](https://github.com/seancorfield/honeysql/issues/419) by adding `honey.sql.protocols` and `InlineValue` with a `sqlize` function.
   * Address [#413](https://github.com/seancorfield/honeysql/issues/413) by flagging a lack of `WHERE` clause for `DELETE`, `DELETE FROM`, and `UPDATE` when `:checking :basic` (or `:checking :strict`).
   * Fix [#392](https://github.com/seancorfield/honeysql/issues/392) by adding support for `WITH` / (`NOT`) `MATERIALIZED` -- via PR [#420](https://github.com/seancorfield/honeysql/issues/420) [@robhanlon22](https://github.com/robhanlon22).
diff --git a/doc/clause-reference.md b/doc/clause-reference.md
index e2b789c..5e74b9a 100644
--- a/doc/clause-reference.md
+++ b/doc/clause-reference.md
@@ -439,7 +439,7 @@ user=> (sql/format '{select * bulk-collect-into [arrv 100] from mytable})
 ["SELECT * BULK COLLECT INTO arrv LIMIT ? FROM mytable" 100]
 ```
 
-## insert-into
+## insert-into, replace-into
 
 There are three use cases with `:insert-into`.
 
@@ -457,6 +457,9 @@ or a table/column specifier and a SQL query.
 For the first and second cases, you'll use the `:values` clause
 to specify rows of values to insert.
 
+`:replace-into` is part of the `:mysql` dialect that produces a `REPLACE INTO`
+statement but otherwise has identical syntax to `:insert-into`.
+
 ```clojure
 ;; first case -- table specifier:
 user=> (sql/format {:insert-into :transport
diff --git a/src/honey/sql.cljc b/src/honey/sql.cljc
index b1843f9..52a8bdb 100644
--- a/src/honey/sql.cljc
+++ b/src/honey/sql.cljc
@@ -94,6 +94,8 @@
   [s x e]
   (str s (str/replace x (str e) (str e e)) e))
 
+(declare register-clause!)
+
 (def ^:private dialects
   (atom
    (reduce-kv (fn [m k v]
@@ -102,7 +104,10 @@
               {:ansi      {:quote #(strop \" % \")}
                :sqlserver {:quote #(strop \[ % \])}
                :mysql     {:quote #(strop \` % \`)
-                           :clause-order-fn #(add-clause-before % :set :where)}
+                           :clause-order-fn
+                           #(do
+                              (register-clause! :replace-into :insert-into :insert-into)
+                              (add-clause-before % :set :where))}
                :oracle    {:quote #(strop \" % \") :as false}})))
 
 ; should become defonce
diff --git a/test/honey/sql_test.cljc b/test/honey/sql_test.cljc
index 9c0c171..686e713 100644
--- a/test/honey/sql_test.cljc
+++ b/test/honey/sql_test.cljc
@@ -968,6 +968,16 @@ ORDER BY id = ? DESC
   (is (= ["SELECT `A``B`"]     (sut/format {:select (keyword "A`B")} {:dialect :mysql})))
   (is (= ["SELECT \"A\"\"B\""] (sut/format {:select (keyword "A\"B")} {:dialect :oracle}))))
 
+(deftest issue-421-mysql-replace-into
+  ;; because the :mysql dialect registers a new clause, and we've probably already run
+  ;; tests with that dialect, we can't test that :replace-into throws an exception when
+  ;; no :dialect is specified because the clause might already be in place:
+  (is (= ["INSERT INTO table VALUES (?, ?, ?)" 1 2 3]
+         (sut/format {:insert-into :table :values [[1 2 3]]})))
+  (is (= ["REPLACE INTO table VALUES (?, ?, ?)" 1 2 3]
+         (sut/format {:replace-into :table :values [[1 2 3]]}
+                     {:dialect :mysql :quoted false}))))
+
 (deftest issue-422-quoting
   ;; default quote if strange entity:
   (is (= ["SELECT A, \"B C\""] (sut/format {:select [:A (keyword "B C")]})))