Chahar (Mongolian: ᠴᠠᠬᠠᠷ/ Чахар; Chinese: 察哈爾; pinyin: Cháhā'ěr), also known as Chaha'er, Chakhar or Qahar, was a province of the Republic of China in existence from 1912 to 1936, mostly covering territory in what is part of Eastern Inner Mongolia.

The area was controlled (in part or fully) by various empires that ruled over China's north including the Han, Tang, Liao, and Jin dynasties.

And ten counties were included from Xuanhua Subprefecture (宣化府), Koubei Circuit (口北道), Hebei Province:[3] All banners belong to the Shilingol League (ᠰᠢᠯᠢ ᠶᠢᠨᠭᠣᠤᠯ, 锡林郭勒盟).

From 1937 to 1945, it was occupied by Japan and made a part of Mengjiang, a Japanese-controlled region led by Mongol Prince Demchugdongrub of the Shilingol Alliance.

The Chahar People's Anti-Japanese Army Alliance (察哈爾民眾抗日同盟軍) was established in Kalgan on May 26, 1933 by Feng Yuxiang (馮玉祥) and Ji Hongchang (吉鴻昌).