USS Lydonia (SP-700) was a 497 gross ton yacht, Lydonia II, acquired from William A. Lydon by the U.S. Navy during World War I. She was outfitted as a patrol craft and spent most of the war based out of Gibraltar, escorting and protecting Allied ships in the Mediterranean and along the Atlantic Ocean coast of Europe. Post-war she was transferred to the U.S. Coast and Geodetic Survey as USCGS Lydonia (CS-302).