The 21 cm Mörser 10 (21 cm Mrs 10) was a heavy howitzer used by Germany in World War I (although classified as a mortar (Mörser) by the German military).

It replaced the obsolete 21 cm Mörser 99, which lacked a recoil system.

Before the 21 cm Mörser 10 was commissioned for mass production, a small test series of 21 cm Versuchmörser 06 ("test mortar") was given to the German army.

Serial number 3 of these rare pieces is now exposed at Red Cliffs, Victoria.

The specifications provided for this weapon by difference sources are contradictory and, thus, those given here cannot be regarded as authoritative.