Catechism of the Catholic Church

When Christ instituted the Twelve, "he constituted [them] in the form of a college or permanent assembly, at the head of which he placed Peter, chosen from among them." Just as "by the Lord's institution, St. Peter and the rest of the apostles constitute a single apostolic college, so in like fashion the Roman Pontiff, Peter's successor, and the bishops, the successors of the apostles, are related with and united to one another." (552, 862)