A full-rigged ship or fully rigged ship is a sailing vessel's sail plan with three or more masts, all of them square-rigged. A full-rigged ship is said to have a ship rig or be ship-rigged.
Sometimes such a vessel will merely be called a ship in 18th- to early-19th-century and earlier usage, to distinguish it from other large three-masted blue-water working vessels such as barques, barquentines, fluyts etc. This full or ship-rig sail plan thus is a term of art that differentiates such vessels as well from other working or cargo vessels with widely diverse alternative sail-plans such as galleons, cogs, sloops, caravels, schooners, brigs and carracks; some of which also have three masted variants (brigs, schooners, sloops, and galleons). The ship-rig sail plan also differs drastically from the large panoply of one and two masted vessels found as working and recreational sailboats.
Alternatively, a full-rigged ship may be referred to by its function instead, as in collier or frigate, rather than being called a ship. In many languages the word frigate or frigate rig refers to a full-rigged ship.