A sailing vessel's rig is its arrangement of masts, sails and rigging. Examples include a schooner rig, cutter rig, junk rig, etc. A rig may be broadly categorized as "fore-and-aft", "square", or a combination of both. Within the fore-and-aft category there is a variety of triangular and quadrilateral sail shapes. Spars or battens may be used to help shape a given kind of sail. Each rig may be described with a sail plan—formally, a drawing of a vessel, viewed from the side.

Modern examples of single-person sailing craft, such as windsurfers, iceboats, and land-sailing craft, typically have uncomplicated rigs with a single sail on a mast with a boom.

In the English language, ships were usually described, until the end of the eighteenth century, in terms of their type of hull design. Using the type of rig as the main type identifier for a vessel became common only in the nineteenth century. This is illustrated by the terminology for ships in the large fleet of colliers that traded to London from the coal ports of the Northeast of England (of which HMS Endeavour was a well-known example). Many of these full-rigged ships (square rigged on all of three masts) had the hull type "bark" – another common classification was "cat". In the second half of the eighteenth century, the square sails on the mizzen were often eliminated. The resulting rig acquired the name of the hull type: initially as "bark" and soon as "barque". This explains the Royal Navy's description of Endeavour as a "cat-built bark".

Each rig may be described with a sail plan—a drawing of a vessel, viewed from the side, depicting its sails, the spars that carry them and some of the rigging that supports the rig. By extension, "sail plan" describes the arrangement of sails on a vessel. A well-designed sail plan should be balanced, requiring only light forces on the helm to keep the sailing craft on course. The fore-and-aft center of effort on a sail plan is usually slightly behind the center of resistance of the hull, so that the sailing craft will tend to turn into the wind if the helm is unattended. The height of the sail plan's center of effort above the surface is limited by the sailing craft's ability to avoid capsize, which is a function of its hull shape, ballast, or hull spacing (in the case of catamarans and trimarans).

Each form of rig requires its own type of sails. Among them are:

Ships that sailed from Europe and the Americas could be categorized in a variety of ways, by number of masts and by sailing rig.

Single-masted sailing vessels include the catboat, cutter and sloop. Two-masted vessels include the bilander, brig, brigantine, ketch, schooner, snow, and yawl. Three-masted vessels include the barque, barquentine, polacre and full-rigged ship. Luggers could have one or two masts and schooners could have two or more masts.

A three-masted vessel has, from front to back, a foremast, mainmast and mizzenmast. A two-masted vessel has a mainmast, the other being a foremast or mizzen. Ships with more than three masts may simply number them or use another scheme, as with the five-masted Preussen.