The Third Council of the Lateran met in March, 1179 as the 11th ecumenical council. Pope Alexander III presided and three hundred and two bishops attended.

Besides removing the remains of the recent antipope schism the council condemned the Waldensian and Cathar heresies and pushed for the restoration of ecclesiastical discipline. Three sessions were held, on 5, 14, and 19 March, in which twenty-seven canons were promulgated. The most important of these were:

• Canon 1 stated that to prevent schisms in future, only cardinals should have the right to elect the pope, and two-thirds of their votes should be required for the validity of an election. If any candidate, after securing insufficient votes, should declare himself pope, both he and his supporters should be excommunicated.
• Canon 2 annulled the ordinations performed by the heresiarchs Octavian (Antipope Victor IV), Guy of Crema, and John de Struma .
• Canon 3 forbade the promotion of anyone to the episcopate before the age of thirty.
• Canon 5 forbade the ordination of clerics not provided with any means of proper support.
• Canon 7 forbade the exaction of money for burial of the dead, benediction, and the administration of the sacraments.
• Canon 9 recalled the military orders of the Knights Templar and the Hospitallers to the observation of canonical regulations.
• Canon 11 forbade clerics to receive women in their houses, or to frequent the monasteries of nuns.
• Canon 19 set the penalty of excommunication for those who levied contributions on churches and churchmen without the consent of the clergy.
• Canon 24 was a prohibition against furnishing the Saracens with material for the construction of their galleys.
• Canon 27 enjoined on princes the repression of heresy.