Haixi Mongolian and Tibetan Autonomous Prefecture (Chinese: 海西蒙古族藏族自治州; Mongolian: ᠬᠠᠶᠢᠰᠢ ᠶᠢᠨ ᠮᠣᠩᠭᠣᠯ ᠲᠥᠪᠡᠳ ᠦᠨᠳᠦᠰᠦᠲᠡᠨ ᠦ ᠥᠪᠡᠷᠲᠡᠭᠡᠨ ᠵᠠᠰᠠᠬᠤ ᠵᠧᠦ; Tibetan: མཚོ་ནུབ་སོག་རིགས་ཆ་བོད་རིགས་རང་སྐྱོང་ཁུལ།), locally also known as Qaidam Prefecture (Mongolian: ᠴᠠᠢᠳᠠᠮ; Tibetan: ཚྭ་འདམ།; Chinese: 柴达木), is an autonomous prefecture occupying much of the northern half of (as well as part of the southwest of) Qinghai Province, China.

It has an area of 325,785 square kilometres (125,786 sq mi) and its seat is Delingha.

After 1949, the People's Government of Dulan County was founded and the area was renamed Dulan Autonomous District (都兰自治区); in 1954, Dulan was renamed Haixi Mongol, Tibetan and Kazakh Autonomous District (海西蒙藏哈萨克族自治区) and in 1955, Haixi Mongol, Tibetan and Kazakh Autonomous Prefecture (海西蒙藏哈萨克族自治州).

In 1963, it was renamed "海西蒙古族藏族哈萨克族自治州" (with the "Tibetan" added to the official county name).

In 1985, after the Kazakhs had returned to Xinjiang, it was again renamed to Haixi Mongol and Tibetan Autonomous Prefecture.