1958 papal conclave

A papal conclave took place from 25 to 28 October following the death of Pope Pius XII on 9 October 1958. On the eleventh ballot, the College of Cardinals elected Cardinal Angelo Giuseppe Roncalli as the new pope. He accepted the election and took the name John XXIII. He was the second patriarch of Venice to be elected pontiff in the 20th century after Pius X.

Some 51 of the 53 cardinals participated as cardinal electors. The Communist governments of Hungary and Yugoslavia prevented the other two from traveling to Rome. In comparison with the conclave of 1922, when three cardinals failed to reach Rome in time for the start of the conclave that opened on the tenth day following the pope's death as required, or that of 1939, when three cardinals reached Rome on the morning the conclave opened under new rules 18 days after the pope's death, all the cardinals who made the trip reached Rome by 22 October with days to spare before the conclave began 16 days after Pius' death. For the first time the speed of travel matched the internationalization of the College of Cardinals, thanks to the advancement in air travel. As one newspaper put it, "the Archbishop of New York can reach Rome today faster than the Archbishop of Palermo did a generation ago". This conclave included cardinals from 21 countries, compared to 16 at the previous conclave, and 21 non-Europeans compared to seven. The 17 Italians out of 51 represented their lowest percentage since 1455.