Mario Alberizzi was born on December 29, 1609 in Salve, Italy, to a noble family, the son of Giovanni Alberizzi, the prince of Vetrana, and Giulia Farnese. His last name is also listed as Albrizj, Alberici, Albericius and Albericci. He belongs to a family with several distinguished cardinals including his maternal uncle, Cardinal Odoardo Farnese, and Cardinal Taddeo Luigi dal Verme. He studied law in Rome where he earned a doctorate in canon and civil law and a master's in theology. After his ordination as a priest, he was appointed in 1638 as Referendary of the Tribunals of the Apostolic Signature of Justice and of Grace. From 1646 to 1650, he served as the governor of the city of Ancona where during a famine, he sold all his possessions to feed the poor. In 1657, he was appointed Canon of the patriarchal Vatican basilica; and from 1657 to 1664, he served as Secretary of the Sacred Congregation of Propaganda Fide. In 1659, he was appointed Voter of the Tribunal of the Apostolic Signature of Grace. In 1664, he was named Voter of the Tribunal of the Apostolic Signature of Grace and Secretary of the S.C. of Bishops and Regulars. In 1669, he was named as canon theologian. He also served as Consultor of the Supreme S.C. of the Roman and Universal Inquisition. On January 19, 1671, he was appointed during the papacy of Pope Clement X as Titular Archbishop of Neocaesarea in Ponto. On January 25, 1671, he was consecrated bishop by Cardinal Federico Borromeo, with Alessandro Crescenzi, Titular Patriarch of Alessandria, and Giacomo Altoviti, Titular Patriarch of Antioch, serving as co-consecrators. On February 2, 1671, he was appointed as Assistant at the Pontifical Throne; and as Apostolic Nuncio to Austria where he served until 1675. On May 27, 1675, he was named by Pope Clement X as cardinal priest and received the title of San Giovanni a Porta Latina on March 23, 1676. On June 22, 1676, he was appointed during the papacy of Pope Clement X as Archbishop of Tivoli. As cardinal, he participated in the conclave of 1676 which elected Pope Innocent XI. He served as Bishop of Tivoli until his resignation on September 4, 1679. He died on September 29, 1680 in Rome and was buried in the chapel of the Basicilica Beata Vergine Maria. He donated his library to the S.C. of Propaganda Fide.
