The Archbishop of Florence, he was born at Florence, March 1, 1389 and died May 2, 1459; known also by his Baptismal name Antoninus (Anthony), which is found in his autographs, in some manuscripts, in printed editions of his works, and in the Bull of canonization, but which has been finally rejected for the diminutive form given him by his affectionate fellow-citizens. His parents, Niccolò and Thomasina Pierozzi, were in high standing, Niccolò beinga notary of the Florentine Republic. At the age of fifteen (1404) Antoninus applied to Bl. John Dominic, the great Italian religious reformer of theperiod, then at the Convent of Santa Maria Novella in Florence, for admission to the Dominican Order. It was not until a year later that he was accepted, and he was the first to receive the habit for the Convent of Fiesole about to be constructed by Bl. John Dominic. With Fra Angelico and Fra Bartolommeo, the one to become famous as a painter, the other as a miniaturist, he was sent to Cortona to make his novitiate under Bl. Lawrence of Ripafratta. Upon the completion of his year in the novitiate, he returned to Fiesole, where he remained until 1409, when with his brethren, all faithful adherents ofPope Gregory XII, he was constrained by the Florentines, who had refused obedience, to take shelter in the Convent of Foligno. A few years later he began his career as a zealous promoter of the reforms inaugurated by Bl. John Dominic. In 1414 he was vicar of the convent of Foligno, thenin turn sub-prior and prior of the convent of Cortona, and later prior of the convents of Rome (Minerva), Naples (Saint Peter Martyr), Gaeta, Sienna,and Fiesole (several times). From 1433 to 1446 he was vicar of the Tuscan Congregation formed by Bl. John Dominic of convents embracing a more rigorous discipline. During this period he established (1436) the famous convent of St. Mark in Florence, where he formed a remarkable community from thebrethren of the convent of Fiesole. It was at this time also that he built with the munificent aid of Cosimo de' Medici, the adjoining church, at the consecration of which Pope Eugene IV assisted (Epiphany, 1441). As a theologian he took part in the Council of Florence (1439) and gave hospitality in St. Mark's to the Dominican theologians called to the council by Eugene IV.

Despite all the efforts of St. Antoninus to escape ecclesiastical dignities, he was forced by Eugene IV, who had personal knowledge of his saintly character and administrative ability, to accept the Archbishopric of Florence. He was consecrated in the convent of Fiesole, 13 march, 1446, and immediately took possession of the see over which he ruled until his death. As he had laboured in the past for the upbuilding of the religious life throughout his Order, so he henceforth laboured for it in his diocese, devoting himself to the visitation of parishes and religious communities, the remedy ofabuses, the strengthening of discipline, the preaching of the Gospel, the amelioration of the condition of the poor, and the writing of books for clergy and laity. These labours were interrupted several times that he might act as ambassador for the Florentine Republic. Ill health prevented him from taking part in an embassy to the emperor in 1451, but in 1455 and again in 1458 he was at the head of embassies sent by the government to the Supreme Pontiff. He was called by Eugene IV to assist him in his dying hours. He was frequently consulted by Nicholas V on questions of Church and State, and was charged by Pius II to undertake, with several cardinals, the reform of the Roman Court. When his death occurred, 2 May, 1459, Pius II gave instructions for the funeral, and presided at it eight days later. He was canonized by Adrian VI, May 31, 1523.