USCGC Spar (WLB-403) was a sea going buoy tender. An Iris class vessel, she was built by Marine Ironworks and Shipbuilding Corporation in Duluth, Minnesota. Spar's preliminary design was completed by the United States Lighthouse Service and the final design was produced by Marine Iron and Shipbuilding. On 13 September 1943 the keel was laid, she was launched on 2 November 1943 and commissioned on 12 June 1944. The original cost for the hull and machinery was $865,941.