Colosteus is an extinct genus of colosteid tetrapod from the Late Carboniferous (late Westphalian stage) of Ohio. Its remains have been found at the Linton site in Saline Township, Ohio, where it is one of the most common tetrapods, and at the Five Points site in Mahoning County, Ohio. It was an elongate, aquatic form with a flattened and pointed head, greatly reduced limbs, two premaxillary tusks, and heavy scalation. It would have reached about 1 m (3.2 ft) in length.