Since 1059, the Cardinals who make up the special College have been the exclusive electors of the Pope.
At present there are 252 Cardinals worldwide. This number includes the former leader of the Catholic Church in Ireland, Seán Brady.
However, Cardinal Brady, having already reached the age of 80 is ineligible to elect the Roman Pontiff or to enter the Conclave.
In total 135 Cardinals meet the criteria to be electors but the maximum number of Cardinals that will have the right to elect the Roman Pontiff is limited.
Any baptized Catholic male is eligible to be elected Pope, however, Pontiffs have traditionally been selected from among the College of Cardinals.
Once the conclave has elected a new Pope the ballots of the Cardinals will be burned and the sending white smoke from the chimney of the Sistine Chapel.
His Reverend Eminence Cardinal Giovanni Battista Re, Dean of the College of Cardinals, will announce the name of the newly elected Supreme Pontiff to the people declaring habemus papam (we have a Pope).
Speculation is mounting over who will replace Pope Francis as the head of the Catholic Church. Among those whose names have been mentioned is Cardinal Kevin Joseph Farrell, Camerlengo of the Holy Roman Church, a Dubliner who until a new Pope is elected has effectively been responsible for the administration of the Catholic Church.
Irish-American Cardinals Seán Patrick O'Malley, Raymond Leo Burke and Timothy Dolan have also been tipped as potential candidates.
Below, in pictures, are some of the front-runners with some biographical detail from the Holy See.
1. Pietro Parolin
Cardinal Pietro Parolin, Secretary of State, was born in Schiavon, Italy, on 17 January 1955. At the age of 14 he entered the seminary of Vicenza and was ordained a priest on 27 April 1980. Particularly expert in matters concerning the Middle East, and more generally in those regarding the geo-political situation of the Asian continent, he has worked specifically to build up and reinforce relations between the Holy See and Vietnam. He also contributed to reopening dialogue between Israelis and Palestinians, convinced of the need for a shared effort to “create the conditions for a true and just peace” in the Middle East. Photo: Getty
2. Luis Antonio Gokim Tagle
Cardinal Luis Antonio Gokim Tagle was born on 21 June 1957 in Manila, the Philippines. He received religious instruction at St. Andrew’s School, Parañaque, then run by the Scheut Missionaries. He was ordained to the diaconate on 18 July 1981 and to the priesthood on 27 February 1982. He participated in the conclave of March 2013, which elected Pope Francis. On 8 December 2019, Pope Francis appointed him Prefect of the Congregation for the Evangelization of Peoples. (Photo by Franco Origlia/Getty Images) Photo: Franco Origlia
3. Péter Erdő
Cardinal Péter Erdő, Metropolitan Archbishop of Esztergom-Budapest, was born in Budapest on 25 June 1952, the first of six children in a family of Catholic intellectuals. He was ordained priest on 18 June 1975 in Budapest. Between 1975-1977 he served in a parish in the city of Dorog. His prodigious systematic reading has led to the publication of more than 250 articles and 25 books in the fields of Canon Law and the medieval history of Canon Law. He has also published a number of cultural and spiritual works. (Photo by Franco Origlia/Getty Images) Photo: Franco Origlia
4. Peter Turkson
Cardinal Peter Kodwo Appiah Turkson was born on 11 October 1948 in Nsuta-Wassaw, Ghana. He attended St. Teresa’s Seminary from 1962-1969 in Amisano and St. Peter’s Regional Seminary in Pedu from 1969-1971. On 20 July 1975 he was ordained for the Archdiocese of Cape Coast. On September 24, 2013, he was confirmed by Pope Francis as President of the Pontifical Council for Justice and Peace. He has been awarded numerous honorary degrees and speaks 6 languages (Fante, English, French, Italian, German, Hebrew). (Photo by Franco Origlia/Getty Images) Photo: Franco Origlia