Assault Support Patrol Boat with forward turret quad Bazooka mounts trialed in Vietnam in 1969

The Assault Support Patrol Boat (ASPB) (also known as the Alpha Boat), was a heavily armed and armored riverine patrol boat developed by the United States Navy for use in the Vietnam War from late 1967.

The ASPB was approximately 50 feet long, its hull was constructed of 7⁄32 inch steel, from the gunwale 2 inches up it was 1⁄8 inch steel, its superstructure was 1⁄4 inch aluminum. The first 36 boats were ordered from Gunderson Brothers Engineering Corporation of Portland, Oregon on 25 October 1966. The initial boats were armed with two Mk 48 turrets with either 20 mm cannon or .50 cal machine guns, two single M60 machine guns or Mk 21 machine guns and one Mk 2 Mod 0/1 .50 cal machine gun/81mm mortar in a well in the aft of the boat, but this well was eliminated in later models. The boat had a complement of five crewmen and could carry up to eight soldiers. The boat was powered by two 430 hp General Motors 12V71 diesel engines giving a top speed of 14.8 knots and it expelled its exhaust directly into the water reducing noise and smoke emissions, making it the quietest river patrol craft. The boat carried some 650 gallons of diesel fuel, allowing an operational range of 130 nautical miles at 10 knots.