A kayak is a small human-powered boat. It typically has a covered deck, and a cockpit covered by a spraydeck. It is propelled by a double-bladed paddle in the hands of a sitting paddler. The kayak was used by the native Ainu, Aleut and Eskimo hunters in sub-Arctic regions of northeastern Asia, North America and Greenland. Modern kayaks come in a wide variety of designs and materials for specialized purposes. Kayaks are in some parts of the world referred to as canoes..

Traditional kayaks typically accommodate one, two or occasionally three paddlers who sit facing forward in one or more cockpits below the deck of the boat. If used, the spraydeck or similar waterproof garment attaches securely to the edges of the cockpit, preventing the entry of water from waves or spray, and making it possible in some styles of boat, to roll the kayak upright again without it filling with water or ejecting the paddler.

Kayaks differ distinctly in design and history from canoes, which are more flat-bottomed boats propelled by single-bladed paddles by a kneeling or sitting paddler, although some modern canoes may be difficult for a non-expert to distinguish from a kayak.