The Patriarchal Cathedral Basilica of Saint Mark, commonly known as St Mark's Basilica, is the cathedral church of the Patriarchate of Venice; it became the episcopal seat of the Patriarch of Venice in 1807, replacing the earlier cathedral of San Pietro di Castello. It is dedicated to and holds the relics of Saint Mark the Evangelist, the patron saint of the city.

The Patriarch of Venice is the ordinary bishop of the Archdiocese of Venice. The bishop is one of only four patriarchs in the Latin Church of the Catholic Church. The other three are the Patriarch of Lisbon, the Patriarch of the East Indies and the Latin Patriarch of Jerusalem. Presently, the only advantage of this purely formal title is the bishop's place of honor in papal processions. In the case of Venice, an additional privilege allows the patriarch, even if he is not a cardinal, the use of the colour red in non-liturgical vestments. In that case, the red biretta is topped by a tuft, as is the custom with other bishops who are not cardinals.