Onguday (Russian: Онгудай) is a rural locality (a selo) and the administrative center of Ongudaysky District of the Altai Republic, Russia, located on the Ursul River, 210 kilometers (130 mi) from the town Gorno-Altaysk, the capital of the republic. Population: 5,655 (2010 Census); 5,376 (2002 Census); 5,399 (1989 Census).