The F-31 Sport Cruiser is a family of American trailerable trimaran sailboats that was designed by New Zealander Ian Farrier and first built in 1991.

[1][2] The F-31 is the production development of the Farrier F-9, which were built by custom shops in small numbers and by amateur builders from plans.

The hull is constructed with a rigid PVC foam core, vacuum bagged moulded to the skins, while the structural beams are reinforced with carbon fiber.

[1][6] The boat is normally fitted with a small outboard motor of typically 9.9 to 15 hp (7 to 11 kW) for docking and maneuvering.

[4] In April 1992 Fred Gan's F-31 Ostac Triumph won the bi-annual Australian Offshore Multihull Championships.