The Convair RIM-2 Terrier was a two-stage medium-range naval surface-to-air missile (SAM), and was among the earliest surface-to-air missiles to equip United States Navy ships. It underwent significant upgrades while in service, starting with a beam-riding system with 10 nm range at a speed of Mach 1.8, and ending as a semi-active radar homing system with a range of 40 nm at speeds as high as Mach 3. It was replaced in service by the RIM-67 Standard ER (SM-1ER).