The Subei Mongol Autonomous County (Chinese: 肃北蒙古族自治县; Mongolian: ᠰᠦᠪᠧᠢ ᠶᠢᠨ ᠮᠣᠩᠭᠣᠯ ᠦᠨᠳᠦᠰᠦᠲᠡᠨ ᠦ ᠥᠪᠡᠷᠲᠡᠭᠡᠨ ᠵᠠᠰᠠᠬᠤ ᠰᠢᠶᠠᠨ) is an autonomous county within the prefecture-level city of Jiuquan in the northwest of Gansu Province, China, bordering Xinjiang to the west, Qinghai Province to the southeast and Mongolia's Govi-Altai Province to the north.

Containing the northernmost point in Gansu, Subei is split into two non-contiguous sections and has an area of 66,748 km2 (25,772 sq mi) and had approximately 13,046 inhabitants in 2000.

To the east it shares a border with Ejin Banner, Alxa League, Inner Mongolia.

In the early 1930s, Birger Bohlin studied the paleontology of the region (then called Taban Buluk).

[1][4] In September 1992, with the approval of the State Council of the People's Republic of China, the only international border crossing in Gansu Province was opened in the Mazongshan area of Subei Mongol Autonomous County.