St Hilarius was born in Sardinia. As archdeacon under Pope Leo I, he fought vigorously for the rights of the Roman See and vigorously opposed the condemnation of Flavian of Constantinople at the Second Council of Ephesus in 449 to settle the question of Eutyches. According to a letter to the Empress Pulcheria collected among the letters of Leo I, Hilarius apologized for not delivering to her the pope's letter after the synod, but owing to Dioscurus of Alexandria, who tried to hinder his going either to Rome or to Constantinople, he had great difficulty in making his escape in order to bring to the pontiff the news of the result of the council.
Pope from 461-468 and guardian of Church unity. He was born in Sardinia, Italy, and was a papal legate to the Robber Council of Ephesus in 449, barely escaping with his life from this affair. Hilary was used by Pope St. Leo I the Great on many assignments. When Leo died, Hilary was elected pope and consecrated on November 19,461. He worked diligently to strengthen the Church in France and Spain, calling councils in 462 and 465. Hilary also rebuilt many Roman churches and erected the chapel of St. John Lateran. He also publicly rebuked Emperor Anthemius in St. Peter's for supporting the Macedonian heresy and sent a decree to the Eastern bishops validating the decisions of the General Councils of Nicaea, Ephesus, and Chalcedon. Hilary consolidated the Church in Sandi, Africa, and Gaul. He died in Rome on February 28.