Marriage in the Catholic Church, also known as holy matrimony, is the "covenant by which a man and woman establish between themselves a partnership of the whole of life and which is ordered by its nature to the good of the spouses and the procreation and education of offspring", and which "has been raised by Christ the Lord to the dignity of a sacrament between the baptised." Catholic matrimonial law, based on Roman law regarding its focus on marriage as a free mutual agreement or contract, became the basis for the marriage law of all European countries, at least up to the Reformation.

The Catholic Church recognizes as sacramental, (1) the marriages between two baptized non-Catholic Christians or between two baptized Orthodox Christians, as well as (2) marriages between baptized non-Catholic Christians and Catholic Christians, although in the latter case, consent from the diocesan bishop must be obtained, with this termed "permission to enter into a mixed marriage". To illustrate (1), for example, "if two Lutherans marry in the Lutheran Church in the presence of a Lutheran minister, the Catholic Church recognizes this as a valid sacrament of marriage." On the other hand, although the Catholic Church recognizes marriages between two non-Christians or those between a Catholic Christian and a non-Christian, these are not considered to be sacramental, and in the latter case, the Catholic Christian must seek permission from his/her bishop for the marriage to occur; this permission is known as "dispensation from disparity of cult".

Weddings in which both parties are Catholic Christians are ordinarily held in a Catholic church, while weddings in which one party is a Catholic Christian and the other party is a non-Catholic Christian can be held in a Catholic church or a non-Catholic Christian church, but in the latter case permission of one's Bishop or ordinary is required for the marriage to be free of defect of form.