Ecclesia Dei or Ecclesia Dei adflicta is the incipit of the motu proprio of 2 July 1988 that Pope John Paul II issued in reaction to the consecration, in spite of an express prohibition by the Holy See, of four bishops by Archbishop Marcel Lefebvre and Bishop Antônio de Castro Mayer in Écône, Switzerland, at the seminary of the Society of St. Pius X (SSPX), an association of priests that Archbishop Lefebvre had founded in 1970 and whose members distrusted the changes then taking place in the Church.
Read more about Ecclesia Dei: Excommunication of The Bishops Involved, Followers of Archbishop Lefebvre, Use of The Tridentine Mass