An Orthodox church is a space used for masses, prayer, and religious ceremonies by any of the Eastern Orthodox faiths descended from the Byzantine church after the schism with Rome in the 11th century. These include the Russian, Greek, Serbian, Macedonian, Romanian, and other orthodox churches, mainly of Eastern Europe and Asia Minor (including Cyprus). The Eastern Orthodox family includes distinct self-governing church bodies; their relationships of communion can be affected by disputes between jurisdictions. This church family is distinct from Oriental Orthodoxy, whose churches did not accept the Council of Chalcedon.

Eastern Orthodox and Oriental Orthodox identify distinct church families. Acceptance of the Council of Chalcedon distinguishes the Eastern Orthodox tradition from the Oriental Orthodox tradition described in the neighboring definition.

The congregation's church affiliation establishes the worship use. A national adjective, an icon, or a dome alone is insufficient to distinguish an Eastern Orthodox church from another church with a similar appearance or cultural setting.