Marcel Lefebvre, French-Swiss archbishop and theologian (d. 1991)
Marcel François Marie Joseph Lefebvre (French: [maʁsɛl fʁɑ̃swa maʁi ʒɔzɛf ləfɛvʁ]; 29 November 1905 – 25 March 1991) was a French Catholic archbishop who greatly influenced modern traditional Catholicism. In 1970, he founded the Society of Saint Pius X (SSPX), a community to train seminarians, in the village of Écône, Switzerland. In 1988, he was excommunicated from the Catholic Church for consecrating four bishops against the express prohibition of Pope John Paul II.

Ordained a diocesan priest in 1929, he had joined the Holy Ghost Fathers for missionary work and was assigned to teach at a seminary in Gabon in 1932. In 1947, he was appointed Vicar Apostolic of Dakar, Senegal, and the next year as the Apostolic Delegate for West Africa. Upon his return to Europe he was elected Superior General of the Holy Ghost Fathers and assigned to participate in the drafting and preparation of documents for the upcoming Second Vatican Council (1962–1965) announced by Pope John XXIII. He was a major leader of the conservative bloc during its proceedings. He later took the lead in opposing certain changes within the church associated with the council. He refused to implement council-inspired reforms demanded by the Holy Ghost Fathers and resigned from its leadership in 1968. In 1970, he founded the Society of Saint Pius X (SSPX) as a small community of seminarians in the village of Écône, Switzerland, with the permission of the local bishop.

In 1975, after a flare of tensions with the Holy See, Lefebvre was ordered to disband the society, but ignored the decision and continued to maintain its activities and existence. In 1988, against the express prohibition of Pope John Paul II, he consecrated four bishops to continue his work with the SSPX. The Holy See immediately declared that he and the other bishops who had participated in the ceremony had incurred automatic excommunication under Catholic canon law, which Lefebvre refused to acknowledge.