GREGORY X. (Tebaldo Visconti), pope from Sept. 1, 1271, to Jan. 1 o, 1276, was born at Piacenza in 1208, and became arch deacon of Liege. While accompanying Edward of England on the crusade, he was elected pope and was consecrated on March 27, 1271. He summoned the i4th general council at Lyons in for the purpose of considering the eastern schism, the condition of the Holy Land, and the abuses in the church. The Greeks were persuaded to consent to a union for the time being, and Rudolph of Habsburg renounced at the council all imperial rights in the States of the Church. Gregory issued the constitution determin ing for the first time the form of conclave at papal elections. He was on his way to Rome to crown Rudolph when he died at Arezzo on Jan. 1 o, 1276.
Gregory's registers were published by J. Guiraud in the Bibli otheque des ecoles francaises d'Athenes et de Rome (1892-98).