Sixth III , 44e Pope (432 - 440).

He is an influential member of the entourage of the popes Zosime then Boniface {{Ier}} and Célestin {{Ier}} and, after having seemed to lean for the Pélagianisme in its youth, he joined with a strict orthodoxy following an exchange of letters with Augustin d' Hippone. Its election the July 31st 432 is thus not a true surprise.

Its action especially illustrates in the policy of construction of religious buildings with the construction of the Holy-Marie-Major Basilique on the site of the basilica built by the pope Libère (352 - 366), one second basilica, that of Saint-Laurent-the-Large, beside that built by the emperor Constantin I {{er}} for the same saint, and finally the Baptistère of Lateran.

In its relationship with the Churches of the East he especially seeks the appeasing after the crisis of the Nestorianisme but defends with strength his prerogatives on the Illyrie vis-a-vis the claims of the Patriarche of Constantinople.

He dies the August 19th 440. Leon {{Ier}} succeeds to him. Its festival for the Catholic church is the March 28th.