The Naval Sea Systems Command (NAVSEA) is the largest of the United States Navy's five "systems commands," or materiel (not to be confused with "material") organizations. NAVSEA consists of four shipyards, nine "warfare centers" (two undersea and seven surface), four major shipbuilding locations and the NAVSEA headquarters, located at the Washington Navy Yard, in Washington D.C.NAVSEA's primary objective is to engineer, build and support the U.S. Navy's fleet of ships and its combat systems.