The century which opened with the pontificate of Gregory VII and closed with that of Alexander III was a momentous period in the history of the councils of the western Church. At no other period in the history of the Church did popes preside so frequently over councils of bishops from all the provinces of the Latin Church, as in the later eleventh century and the twelfth century. Some of these councils played a notable role in shaping events: Urban II's council of Clermont (1095), at which the First Crusade was launched; Calixtus II's council of Rheims (1119), which attempted to solve the problem of investitures; Eugenius III's council of Rheims (1148), concerned both with the defence of orthodoxy and with the affairs of the English church and kingdom; Alexander III's council of Tours (1163), held in the midst of schism and likewise concerned to defend orthodoxy. Most imposing of all, by virtue of the number of their participants and of the definitive character of their legislation, were the three Lateran councils of 1123, 1139 and 1179, called ‘ecumenical’ in the tradition of the Latin Church.

The ‘general’ and ‘ecumenical’ councils of this period developed out of two very different kinds of assembly. The first of these antecedents was the papal synod of the pre-reform period. This was a synod attended mainly by the suburbican bishops, sometimes also by the other bishops of the Roman ecclesiastical province and very occasionally by bishops from those regions of Italy not under Byzantine control.