Bayanday is a rural locality located in Russia. It serves as the administrative center of the Bayandayevsky District within the Ust-Orda Buryat Okrug of Irkutsk Oblast.
According to census data, the population of the settlement has fluctuated over recent decades. The 2010 census recorded a population of 2,672, following figures of 2,874 in 2002 and 3,383 during the 1989 Soviet census.