Simultaneum

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 (such as Roman Catholic, Lutheran, Reformed, or United, etc.), share the same church building, although they worship at different times and with different clergy. Simultaneums have been seen as a manifestation of Christian ecumenism.

Simultaneum as a policy was particularly attractive to Christian rulers who ruled over populations which contained considerable numbers of both Catholics and Protestants. It was often the opposite of cuius regio, eius religio and used in situations where a ruler was of a different religion than the majority of the people, and not strong enough to impose his religion on the population. These have been seen as a form of religious toleration.