Windsurfing or sailboarding is a surface water sport that combines elements of surfing and sailing. It consists of a board usually two to four metres long, powered by wind on a sail. The rig is connected to the board by a free-rotating universal joint and comprises a mast, wishbone boom and sail. The sail area ranges from less than 2.5 m² to more than 12 m² depending on the conditions, the skill of the sailor and the type of windsurfing being undertaken.

The history of windsurfing began in 1948 on the Susquehanna River, Pennsylvania, USA when Newman Darby invented the sailboard which incidentally, he did not patent. In 1964, Darby began selling his sailboards.

Windsurfing can be said to straddle both the laid-back culture of surf sports and the more rules-based environment of sailing. Although it might be considered a minimalistic version of a sailboat, a windsurfer offers experiences that are outside the scope of any other sailing craft design. Windsurfers can perform jumps, inverted loops, spinning maneuvers, and other "freestyle" moves that cannot be matched by any sailboat. Windsurfers were the first to ride the world's largest waves, such as Jaws on the island of Maui, and, with very few exceptions, it was not until the advent of tow-in surfing that waves of that size became accessible to surfers on more traditional surfboards. Extreme waves aside, many expert windsurfers will ride the same waves as wavesurfers do (wind permitting) and are themselves usually very accomplished without a rig on a conventional surfboard.