Conclavism is the practice that has existed since the second half of the 20th century which consists in the convening of a conclave to elect rival popes (antipopes) to the current pope of Rome. This method is used by some Catholics, often Sedevacantists, who do not accept the legitimacy of their present papacy. Those who hold the position that a conclave can be convened to elect a pope to rival the current pope of Rome are called conclavists.^[1]

This claim is usually associated with the claim, known as sedevacantism, that the present holder of the title of pope is not pope, which implies they consider they have the right to elect a pope. But not all Sedevacantists are Conclavists.^[1]

The term "Conclavism" comes from the word "conclave", the term for a meeting of the College of Cardinals convened to elect a bishop of Rome, when that see is vacant.

Conclavism is different from what George Chryssides calls the "mysticalists" phenomenon, i.e. people declaring themselves popes after receiving a personal mystical revelation. This is because in the mysticalists' cases no human institution is used to have a pope appointed; an example of this case is the Apostles of Infinite Love.^[1]

The description and explanation of conclavism of George Chryssides is:^[1]

Since most sedevacantists (although not all) object to Pope John XXIII's modernization of the Roman Catholic Church, they argue that he nullified his appointment to the papacy in 1958. It is therefore inferred that the conclave of cardinals who elected him was also invalid. Conclavists, however, hold that the method of electing a pope by a conclave remains the valid process and hence that it is necessary for a conclave to be reconstituted and convened. Since none of the members of that Pope John XXIII conclave remain alive, one must resort to the principle of epikeia ('reasonableness'), and that membership of a conclave should be drawn from the faithful community who are invited.

The idea of "reconvening a conclave arose in the late 1960s and early 1970s". One of the first proponents of the idea was Joaquín Sáenz y Arriaga, a Mexican priest.^[1]

In the late 1980s David Bawden promoted the idea of a papal election and ultimately sent out over 200 copies of a book of his to the editors of all the sedevacantist publications he could find, and to all the priests listed in a directory of traditionalists as being sedevacantists.^[2] He was then elected in 1990 by a group of six people who included himself and his parents, and took the name "Pope Michael".^[3][1]

• Pope Michael I. David Allen Bawden. In 1990 six people, which included Bawden's parents, elected Bawden who took the name Pope Michael.^[1][4] He died on 2 August 2022 and was succeeded by Rogelio Martinez, who took the name of Pope Michael II, in July 2023.^[5]
• Pope Linus II. Another conclave, this time held in Assisi, Italy in 1994, elected the South African Victor von Pentz, an ex-seminarian of the Society of St Pius X, as Pope Linus II. Linus took up residence in Hertfordshire, England.^[1][6] Some sources claim he may have resigned the position around 2007.^[7][8]
• Pope Pius XIII. In October 1998, the U.S.-based True Catholic Church elected Friar Lucian Pulvermacher as Pope Pius XIII.^[1] He died on 30 November 2009. No successor has been named since his death.
• Pope Leo XIV. On 24 March 2006 a group of 34 elected the Argentine Oscar Michaelli as Pope Leo XIV. On his death in 2007, Leo XIV was succeeded by Juan Bautista Bonetti, who took the name of Pope Innocent XIV, but resigned three months later. He was succeeded by Alejandro Tomas Cardinal Greico, who took the name of Pope Alexander IX.^[1][9]

• Antipope
• Sedevacantism
• Sedeprivationism
• Episcopi vagantes
• Independent Catholic Churches
• Traditionalist Catholic
• Palmarian Christian Church