Kamen-na-Obi, city and administrative centre of Kamensky rayon (sector), Altay kray (territory), south-central Russia. A port on the Ob River, it was founded in 1670 and designated an urban settlement in 1915 and became a city in 1925. Its economic base is the food-processing industry; other factories produce bricks and furniture. Teacher-training and veterinary colleges are located in the city. Pop. (2006 est.) 45,140.