The Viper 640 is an American trailerable sailboat, that was designed by Brian Bennett for racing and first built in 1996.

The result is a small recreational planing keelboat, built predominantly of fiberglass, with carbon fiber spars.

It has a fractional sloop rig, a plumb stem, an open transom, a transom-hung rudder and a lifting fin daggerboard-style keel, with a weighted bulb, with 220 lb (100 kg) of lead ballast.

The design displaces 750 lb (340 kg) and is equipped with an asymmetrical spinnaker of 425 sq ft (39.5 m2) for downwind sailing.

[3][7] Cruising World magazine named the design Overall Boat of the Year and top Performance One-Design of 2002, stating "the panelists agreed that the Viper is inherently simple, offers quality construction at a great price, and is extremely fun to sail.