| Type: | Bishop |
| Honorific-Prefix: | Most Reverend |
| Ambrosius Catharinus | |
| Bishop of Minori | |
| Church: | Catholic Church |
| Term: | 1546–1552 |
| Predecessor: | Giovanni Pietro De Bono |
| Successor: | Antonio Simeoni |
| Ordination: | 27 Aug 1517 |
| Consecration: | 21 Dec 1546 |
| Birth Date: | 1484 |
| Death Place: | Naples |
Lancelotto Politi (religious name Ambrosius Catharinus, 1483 - 1553) was an Italian Dominican canon lawyer, theologian and bishop.
The 1913 Catholic Encyclopedia describes Catharinus as a "brilliant eccentric", and asserts that, despite frequent accusations of heresy, his teachings were always "within the bounds of orthodoxy".
Politi was born at Siena. At sixteen he became Doctor of Civil and Canon Law (J.U.D.) in the academy of Siena. After visiting many academies in Italy and France he was appointed (1508) a professor at Siena, and had among his pupils Giovanni del Monte, afterwards Pope Julius III, and Sixtus of Siena, a converted Jew who esteemed his master, yet severely criticized some of his writings.
About 1513 he entered the Order of St. Dominic in the convent of St. Mark, at Florence. He studied scripture and theology without a master. This may account for his independence, and his defence of opinions which were singular, especially in regard to predestination, the certitude of possessing grace, the residence of bishops in their dioceses, and the intention required in the minister of a sacrament.
He was a strenuous defender of Catholicism against Martin Luther and his followers; and was prominent in the discussions of the Council of Trent, to which he was called by his former pupil, Cardinal del Monte, legate of Paul III. In the third, public, session (4 February 1546), Catharinus, pronounced a notable discourse, later published ["Oratio ad Patres Conc. Trid." (Louvain, 1567; Paris, 1672)].
Notwithstanding attacks upon his teaching he was appointed Bishop of Minori in 1546, and, in 1552, Archbishop of Conza, Province of Naples. Pope Julius III, successor of Paul III, called Politi to Rome, intending, says Jacques Échard, to elevate him to the cardinalate, but he died before reaching Rome.
Pallavicino and other authorities declare that the Council of Trent did not condemn his singular opinions. He defended the Immaculate Conception of the Blessed Virgin. According to Échard, he regretted towards the end of his life the vehemence with which he had combatted Cardinal Cajetan and Father Dominic Soto. He died at Naples.
His principal works (for complete list see Echard) are:
He also published numerous opuscula, e. g., on Providence and predestination, on the state of children dying without baptism; on giving communion to young children; on celibacy; on the Scriptures and their translation into the vernacular.