Hulun Lake, Nature reserve and freshwater lake in Inner Mongolia, China

Hulun Lake is a freshwater nature reserve in Inner Mongolia that forms a large irregular rectangle across the Hulunbuir Grassland. The water basin sits low in a flat landscape bordered by endless grass, stretching from the southwest toward the northeast.

The Dalai Lake Nature Reserve was established in 1986 and upgraded to national status in 1992; in 2014 it was renamed the Hulun Lake National Nature Reserve. In 1994 China, Mongolia and Russia joined their reserves into the CMR Dauria International Protected Area. The lake was listed as a Ramsar wetland and a UNESCO biosphere reserve in 2002.

The name Hulun comes from the Mongolian word for otter, as both Hulun and nearby Buir Lake once held many otters; Buir means male otter. Herders call the lake Dalai Nur, "sea lake". The 901-type supply ship Hulun Lake is named after it.

The lake is best visited from spring through autumn when weather conditions are mild and paths are easy to walk. Visitors should know the area is quite windy, so warm clothes and sun protection are important to bring.

The lake has no surface outlet in most years; only when precipitation is high does it overflow at the northern shore and reach the Argun River after about 30 kilometres. Its main inflows are the Kherlen River, rising in Mongolia, and the Uldz, which drains Buir Lake. The connecting Zhalan'eluomu River is a two-way channel: when the Hailar River runs higher, its water enters Hulun Lake; when lower, lake water drains out toward the Argun.