Ecclesiastical polity is the operational and governance structure of a church or of a Christian denomination. It also denotes the ministerial structure of a church and the authority relationships between churches. Polity relates closely to ecclesiology, the study of doctrine and theology relating to church organization.
Issues of church governance appear in the first chapters of the Acts of the Apostles; the first act recorded after the ascension is the election of Matthias as one of the Twelve Apostles, replacing Judas Iscariot. Over the years, a system of episcopal polity developed.
During the Protestant Reformation, reformers asserted that the New Testament prescribed structures different from those of the Roman Catholic Church of the day and different Protestant bodies used different types of polity. During this period Richard Hooker wrote Of the Laws of Ecclesiastical Polity (published 1594–1597) to defend the polity of the Church of England against views of the Puritans.
Ecclesiastical polity is used in several closely related senses. Most commonly it refers to the field of church governance in the abstract, but it also can refer to the governance of a particular Christian body. In this sense it is used as a term in civil law. Polity is sometimes used as a shorthand for the church governance structure itself.