Bayandayevsky District (Russian: Баянда́евский райо́н; Buryat: Баяндайн аймаг, Baiandain aimag) is an administrative district of the Ust-Orda Buryat Okrug of Irkutsk Oblast, Russia, one of the thirty-three in the oblast.

[6] It is located in the southern part of the oblast.

The area of the district is 3,756.2 square kilometers (1,450.3 sq mi).

[3] Its administrative center is the rural locality (a selo) of Bayanday.

[10] The population of Bayanday accounts for 23.2% of the district's total population.