Portsmouth Naval Shipyard (Portsmouth Navy Yard)

Portsmouth Naval Shipyard is a United States Navy shipyard on Seavey's Island in Kittery, Maine, on the Piscataqua River, opposite Portsmouth, New Hampshire. The river's tidal current keeps the channel to the Atlantic free of ice year-round. The yard is one of four public shipyards operated by the Navy and is the oldest continuously operating.

Work at the yard is centred on the overhaul, refuelling and modernisation of nuclear-powered attack submarines; the yard no longer builds ships. Its industrial workload consists of docking and non-docking availabilities on Los Angeles-, Seawolf- and Virginia-class boats. The shipyard employs several thousand federal civilian workers, supplemented by contractor personnel from firms including Delphinius Engineering, Oceaneering International, Orbis Sibro and Q.E.D. Systems. The command is headed by a Navy captain. Portsmouth Naval Shipyard received the Meritorious Unit Commendation in 2005 for service between September 2001 and August 2004.

The installation occupies roughly 278 acres and comprises dry docks, waterfront berthing and industrial shops. Dry Dock 1 has been extended and fitted with a super flood basin, additional crane rails and high-capacity dewatering pumps; Dry Dock 2 has undergone crane rail upgrades and complex reconstruction. Building 178 provides waterfront support for Virginia-class submarines. The United States Army New England Recruiting Battalion relocated to the yard in June 2010 from the closed Naval Air Station Brunswick. The United States Coast Guard homeports the medium-endurance cutters Reliance, Tahoma and Campbell at the yard. The site was listed on the EPA National Priorities List in 1994 following detection of PCB, PAH, metals and benzene contamination in groundwater, soil and sediment, and was removed from the list in 2024 after remediation.

The shipyard was established on 12 June 1800 under Navy Secretary Benjamin Stoddert as the first federal navy yard, on Fernald's Island. Submarine construction began during the First World War with L-8, the first submarine built by a U.S. navy yard, and expanded to more than seventy boats in the Second World War, after which the yard became the Navy's centre for submarine design and development. Swordfish, its first nuclear-powered submarine, was launched in 1957, and Sand Lance in 1969 was the last hull built there. Closure orders issued in 1965 were rescinded in 1971, and a 2005 BRAC closure recommendation was reversed in August 2005.