HMS Preventer (Z265) was a net laying ship for the Royal Navy during the Second World War acquired from the United States Navy in September 1944 via Lend-Lease. The ship was laid down as Seagrape (YN-90), a net tender of the Ailanthus class, on 20 May 1943 at the American Car and Foundry Co. in Wilmington, Delaware. On 17 January 1944, while still under construction, the ship was reclassified as a net laying ship and redesignated AN-77. Seagrape was launched on 9 August and completed on 30 September.