CELESTINE II., pope in 1143-1144. Guido del Castello, born of noble Tuscan family, able and learned, studied under Abelard and became a cardinal priest. He was pope from Sept. 26, 1143 to March 8, 1144. He removed the interdict which Innocent II. had employed against Louis VII. of France.
See A. Certini, Vita (Foligno, 1716) ; Migne, Patrol. Lat. 179, 765-820; Jaffe, Regesta Pontificum Romanorum (1888) , vol. ii., I ff.