Cardinal Eugenio Pacelli is elected Pope and takes the name Pius XII.

A cardinal is a senior member of the clergy of the Catholic Church. As titular members of the clergy of the Diocese of Rome, they serve as advisors to the pope, who is the bishop of Rome and the visible head of the worldwide Catholic Church. Cardinals are chosen and formally created by the pope, and typically hold the title for life. Collectively, they constitute the College of Cardinals. The most solemn responsibility of the cardinals is to elect a new pope in a conclave, almost always from among themselves, with a few historical exceptions, when the Holy See is vacant.

A conclave was held on 1 and 2 March 1939 to elect a new pope to succeed Pius XI, who had died on 10 February. All 62 eligible cardinal electors attended. On the third ballot, the conclave elected Cardinal Eugenio Pacelli, the camerlengo of the Apostolic Chamber and cardinal secretary of state. After accepting his election, he took the name Pius XII.

Pope Pius XII was the head of the Catholic Church and sovereign of the Vatican City State from 2 March 1939 until his death on 9 October 1958. He is the most recent pope to take the pontifical name "Pius".

March 2 is the 61st day of the year in the Gregorian calendar; 304 days remain until the end of the year.