A Thames sailing barge is a type of commercial sailing boat once common on the River Thames in London. The flat-bottomed barges, with a shallow draught and leeboards, were perfectly adapted to the Thames Estuary, with its shallow waters and narrow tributary rivers. The larger barges were seaworthy vessels, and were the largest sailing vessel to be handled by just two men. The average size was about 120 tons and they carried 4,200 square feet (390 m2) of canvas sail in six working sails. The mainsail was loose-footed and set up with a sprit, and was brailed to the mast when not needed. It is sheeted to a horse, as is the foresail; they require no attention when tacking. The foresail is often held back by the mate to help the vessel come about more swiftly.

Barge often refers to a flat-bottomed inland waterway vessel which does not have its own means of mechanical propulsion. The first modern barges were pulled by tugs, but on inland waterways, most are pushed by pusher boats, or other vessels. The term barge has a rich history, and therefore there are many other types of barges.