The Penitential Act is a Christian form of general confession of sinfulness that normally takes place at the beginning of the celebration of Mass in the Roman Rite of the Catholicism, as well as in Lutheranism.

The Confiteor is one of the prayers that can be said during the Penitential Act at the beginning of Mass of the Roman Rite in the Catholic Church. It is also said in the Lutheran Church at the beginning of the Divine Service, and by some Anglo-catholic Anglicans before Mass.