The Euchologion is one of the chief liturgical books of the Eastern Orthodox and Byzantine Catholic churches, containing the portions of the services which are said by the bishop, priest, or deacon. The Euchologion roughly corresponds to a combination of the missal, ritual, and pontifical as they are used in Latin liturgical rites. There are several different volumes of the book in use.

A liturgical book, or service book, is a book published by the authority of a church body that contains the text and directions for the liturgy of its official religious services.