In sailing, a bermuda rig is:

• A rig of mainsail or course that consists of a triangular sail set aft of the mast, with its head raised to the top of the mast, its luff running down the mast and normally attached to it for all its length, its tack attached at the base of the mast, its foot controlled by a boom, and its clew attached to the aft end of the boom, which is controlled by its sheet.
• A rig that uses such a bermuda mainsail.

This sail, whether set as a mainsail on the main mast or as the course (the principal sail) on another mast, is known as a bermuda sail. Originally developed for the bermuda sloop, it has largely replaced the older gaff rigged fore and aft sails.

A bermuda rigged sloop with exactly one jib is known as a bermuda sloop, marconi sloop or marconi rig. Bermuda sloop can also refer to a more specific type of vessel.

The foot of a bermuda sail may be attached to the boom along its length, or in more modern rigs the sail is attached to the boom only at its ends. This modern variation of a bermuda mainsail is known as a loose-footed main.

The main controls on a bermuda sail are:

• The halyard used to raise the head, and sometimes to tension the luff.
• The outhaul used to tension the foot by hauling the clew towards the end of the boom.
• The sheet used to haul the boom down and towards the center of the boat.
• The vang or kicking strap which runs between a point partway along the boom and the base of the mast, and is used to haul the boom down when on a run.

Minor (but vital when they are present) controls include:

• A downhaul on the boom at the mast end, used to set sail height and sometimes tension.
• A cunningham's eye, particularly useful for getting a good shape in an older sail in medium to strong winds.
• A leach line, eased for lighter winds.
• Batten tension controls, eased for lighter winds but only accessible before the sail is raised.
• Reefing points and lines, used to reduce sail area in strong winds.
• A gybe preventer, used when running.
• Backstay tension controls to control mast bend.
• Running backstays to fine tune the shape of the mast.

The tension of the jib halyard(s) will also particularly affect the shape of the mast and therefore the set of the bermuda sail, and of course the set of all other sails will have some affect on it.