The Sisu-class motor torpedo boats (English: Guts) was a series of two Italian MAS type motor torpedo boats of the Finnish Navy.

Sisu and Hurja were purchased by the Finns in 1920, and saw service in World War II.

[1] When dashing forward at full speed, the vessels sprayed water high in the air, earning the nickname "the fountains" from Finnish sailors.

On 1 October 1941 Sisu, together with Nuoli, was patrolling east of Gogland when it came across a large, stationary Soviet minesweeper of the Fugas class.

Sisu missed with her first torpedo, having mistaken the foam painted on the minesweeper's bow for an indication that it was actually moving.