The Portsmouth Naval Shipyard, often called the Portsmouth Navy Yard, is a United States Navy shipyard on Seavey's Island in Kittery, Maine, bordering Portsmouth, New Hampshire. The naval yard lies along the southern boundary of Maine on the Piscataqua River.

A shipyard, also called a dockyard or boatyard, is a place where ships are built and repaired. These can be yachts, military vessels, cruise liners or other cargo or passenger ships. Compared to shipyards, which are sometimes more involved with original construction, dockyards are sometimes more linked with maintenance and basing activities. The terms are routinely used interchangeably, in part because the evolution of dockyards and shipyards has often caused them to change or merge roles.