Fish locomotion is the various types of animal locomotion used by fish, principally by swimming. This is achieved in different groups of fish by a variety of mechanisms of propulsion, most often by wave-like lateral flexions of the fish's body and tail in water, and in various specialised fish by motions of the fins. The major forms of locomotion in fish are:

• Anguilliform, in which a wave passes evenly along a long slender body;
• Sub-carangiform, in which the wave increases quickly in amplitude towards the tail;
• Carangiform, in which the wave is concentrated near the tail, which oscillates rapidly;
• Thunniform, rapid swimming with a large powerful crescent-shaped tail; and
• Ostraciiform, with almost no oscillation except of the tail fin.

More specialized fish include movement by pectoral fins with a mainly stiff body, opposed sculling with dorsal and anal fins, as in the sunfish; and movement by propagating a wave along the long fins with a motionless body, as in the knifefish or featherbacks.

In addition, some fish can variously "walk" (i.e., crawl over land using the pectoral and pelvic fins), burrow in mud, leap out of the water and even glide temporarily through the air.