Altkirch (French: [altkiʁʃ] , German: [ˈaltkɪʁç]; Alsatian: Àltkìrech) is a commune in the Haut-Rhin department in Alsace in north-eastern France.

The town is traditionally regarded as the capital of Sundgau.

The name of the commune means old church (Alsatian: Àlta Kìrch or Àlta Kìrech; German: Alte Kirche).

In the 1370s, the citizens of Altkirch battled and won against a company of Gugler mercenaries.

Its inhabitants are known as Altkirchois.

The resident population number of 5500 is rather deceptive as some 15,500 people will be in town on a typical working day (4500 working, 3000 studying, 3000 for medical treatment and another 5000 divided between shopping, administrative offices, cultural and sporting activities).