Marcel François Marie Joseph Lefebvre was a French Catholic archbishop who influenced modern traditional Catholicism. In 1970, five years after the close of the Second Vatican Council, he founded the Society of Saint Pius X (SSPX), a community to train seminarians in the traditional manner, in the village of Écône, Switzerland. In 1988, Pope John Paul II declared that Archbishop Lefebvre had "incurred the grave penalty of excommunication envisaged by ecclesiastical law" for consecrating four bishops against the pope's express prohibition but, according to Lefebvre, in reliance on an "agreement given by the Holy See ... for the consecration of one bishop."

The Society of Saint Pius X is a canonically irregular traditionalist Catholic fraternity of priests founded in 1970 by Archbishop Marcel Lefebvre. Lefebvre was a leading traditionalist at the Second Vatican Council with the Coetus Internationalis Patrum and Superior General of the Holy Ghost Fathers until 1968. The society was initially established as a pious union of the Catholic Church with the permission of François Charrière, the Bishop of Lausanne, Geneva and Fribourg in Switzerland.