The Missa brevis in D minor, K. 65/61a, is a mass composed by Wolfgang Amadeus Mozart (12 years old at the time) and completed on 14 January 1769.

[1] It is scored for SATB soloists and choir, violin I and II, 3 trombones colla parte, and basso continuo.

It is thought that this mass was performed in the University of Salzburg's Kollegienkirche to open a forty-hour vigil.

[2][3] As a Lenten mass, it is likely that the Gloria could not have been performed on this occasion, and would have been composed for subsequent use.

[4] This is Mozart's shortest setting of the Order of Mass, and his only missa brevis set in a minor key.