Kamen-na-Obi (Russian: Ка́мень-на-Оби́), known until 1933 as Kamen (Ка́мень), is a town in Altai Krai, Russia, located on the left bank of the Ob River 208 kilometers (129 mi) northwest of Barnaul, the administrative center of the krai. Population: 43,888 (2010 Census);44,375 (2002 Census);42,483 (1989 Census); 36,000 (1970).
It was founded in 1751 as the village of Kamen (Камень) and granted town status in 1915.
Within the framework of administrative divisions, Kamen-na-Obi serves as the administrative center of Kamensky District, even though it is not a part of it. As an administrative division, it is, together with one rural locality (the station of Plotinnaya), incorporated separately as the town of krai significance of Kamen-na-Obi—an administrative unit with the status equal to that of the districts. As a municipal division, the town of krai significance of Kamen-na-Obi is incorporated as Kamen-na-Obi Urban Okrug.
The main industries are food-processing and brick and furniture manufacture.