Concordat, a treaty or agreement entered into by the see of Rome with a secular prince or government, touching one or more points of ecclesiastical discipline. The Roman Catholic church is governed by her own laws and observances in all matters not definitely settled by Christ or his apostles. (See Canon Law).

Concordats are simply the arrangement by treaty of such laws and observances as lie outside the verge of divine law; the ecclesiastical power whereby similar laws and observances were established moulding and modifying them to meet the varying mutations of human affairs, and the different requirements of time and place. The name was probably first used in 1418, being applied to the stipulations entered into by Martin V. on the one side, and England, Germany, and France on the other. The most notable concordat of modern times was that between Pius VII. and Bonaparte in 1801, by which the Christian religion, which had been formally abolished by the revolutionary leaders, was reestablished in France. Late instances of concordats are those made with Austria in 1855, Wilrtemberg in 1857, and Portugal in 1859.