Bayandelger (Mongolian: Баяндэлгэр, Rich expanse) is a sum (district) of Sükhbaatar Province in eastern Mongolia.

The population (as of 2009) of the sum is 4,569, including 1,169 in the sum center.

[2] Bayandelger has a cold semi-arid climate (Köppen climate classification BSk) with warm summers and very cold winters.

Most precipitation falls in the summer as rain.

Winters are very dry.