For the plant genus Knightia, see Knightia (plant)

Knightia is an extinct genus of fish well-known from abundant fossils found in the Green River Formation of Wyoming. They rarely exceeded 25 cm in length and are found throughout the formation.

Knightia was a slender fish and seems to have been a secondary consumer, feeding mainly on ostracods, algal forms and diatoms, as well as some smaller fish. They were schooling fish, and because of this they are frequently found together in mass mortality layers. The tendency for individual fishes to cluster in groups was probably quite common. Modern forms of small fish are noted for schooling, and it is highly probable that the ancient types associated similarly.

Knightia were abundant and important because they were included in the diets of most of the Green River Formation's larger fishes. They were double scuted, having rows of dorsal and ventral scutes running from the posterior end of the head back to the median fins.