The Sisu class motor torpedo boats () was a series of two Italian M.A.S. type motor torpedo boats of the Finnish Navy. The vessels were constructed in 1916 by the Orlando shipyard in Livorno, Italy. Sisu and Hurja were purchased by the Finns in 1920, and saw service in World War II. When dashing forward at full speed, the vessels sprayed water high in the air, earning the nickname "the fountains" from Finnish sailors.