A shared church, simultaneum mixtum, a term first coined in 16th-century Germany, is a church in which public worship is conducted by adherents of two or more religious groups. Such churches became common in the German-speaking lands of Europe in the wake of the Protestant Reformation. The different Christian denominations, share the same church building, although they worship at different times and with different clergy. It is thus a form of religious toleration.

The Church of Old Saint Peters is a by simultaneum Catholic and Lutheran church building in Strasbourg, Alsace is first mentioned in 1130.