Until the French Revolution, the parishes now contained in the diocese of Pontoise had belonged to several dioceses of the
ancien regime: Rouen, Paris, Beauvais and Senlis. As a result of the creation of the system of "
departments," Pontoise became part of the diocese of Versailles, called the diocese of Seine-et-Oise in the constitutional church (1791–1801). The diocese of Pontoise was created by
Pope Paul VI, in the bull "Qui Deo Volente," on 9 October 1966, in carrying out the norms established by the
Second Vatican Council (1962–1965), as part of a restructuring of the two very populous dioceses of Paris and Versailles. It was also made desirable due to the redrawing of civil boundaries in the region of Paris. The first bishop of Pontoise, André Rousset, was appointed by the pope on 9 October 1966. He had previously been titular bishop of Vaga (Africa Proconsularis, Tunisia) and Auxiliary Bishop of Versailles (1963–1966). The first
ordinations of new priests since its founding in 1966 occurred in 2011, when four men were ordained priests for the diocese. The bull of foundation had required that all seminarians belonged to the diocesan territory in which they had their legal residence or in which the parish to which they belonged was situated. == Cathedral ==