Society of Saint Pius X

The Society of Saint Pius X (SSPX; Latin: Fraternitas Sacerdotalis Sancti Pii X, lit.'Priestly Fraternity of Saint Pius X', FSSPX) is a traditionalist Catholic organization founded in 1970 by Archbishop Marcel Lefebvre. Considered schismatic by the Catholic Church, the society comprises priests and seminarians and is associated with a worldwide network of chapels, schools, religious communities, and lay supporters. It is known for its opposition to several reforms associated with the Second Vatican Council. Adherents to the SSPX are called Lefebvrists, Lefebvrians, or Lefebvrites, terms SSPX rejects.

The Holy See formally declared the SSPX and its adherents to be in schism and excommunicated them in 1988 and in 2026, each time following illicit consecrations of bishops by the SSPX. The SSPX considers itself never to have been excommunicated nor to be or have been in schism.

Named after Pope Pius X for his anti-modernist stance, the society retains the Tridentine Mass and pre-Vatican IIliturgical books in Latin. It has more than 700 priests among 1,482 total members. Estimates of the number of laypeople who attend SSPX Masses vary significantly.