Mar Bechara Boutros al-Rahi was born in Himlaya, Matn District, Lebanon on 25 February 1940. He attended Collège Notre Dame de Jamhour, a Jesuit school in Lebanon. He entered the Mariamite Maronite Order on 31 July 1962 and was ordained as a priest on 3 September 1967. From 1967 to 1975 he was responsible for the Arabic programs of Vatican Radio. In 1975, he received a PhD in canon and civil law. He also studied for three years at Lateran University in Rome.
At 71, he was elected patriarch of the Maronites on 15 March 2011, after getting more than two-thirds of the votes of the 39 bishops and replacing Nasrallah Sfeir. The new patriarch formally requested and received ecclesiastical communion from Pope Benedict XVI on 24 March 2011 pursuant to Canon 76 § 2 of the Code of Canons of the Eastern Churches. The Mass for the inauguration of his Patriarchate took place on 25 March 2011, in Bkerké, the see of the Maronite Catholic Patriarchate. As is customary for all Maronite Patriarchs, Patriarch al-Rahi took the additional name Boutros, that of Saint Peter, who briefly held the See of Antioch before moving to Rome to become Bishop there.
On 31 January 2013, Cardinal Patriarch al-Rahi was appointed by Pope Benedict XVI to serve as a member of the Congregation for the Oriental Churches, the Supreme Tribunal of the Apostolic Signatura, the Pontifical Council for the Pastoral Care of Migrants and Itinerants, and the Pontifical Council for Social Communications. In February 2013, Patriarch Rai, being a Cardinal, became a candidate to the papacy. He participated as a cardinal elector in the conclave that elected Pope Francis. Cardinal Rai was one of four cardinal-electors from outside the Latin Church who wore distinct vestments proper to their respective churches. The other three cardinal-electors from outside the Latin Church were Coptic Catholic Patriarch-Emeritus Antonios Naguib, Syro Malabar Major Archbishop George Alencherry, and Syro-Malankara Major Archbishop Baselios Cleemis. Cardinal Rai's attire during the opening day was distinct from most of the other electors in that he wore all-red vestments with distinct headgear proper to the Maronite Church. Cardinal Rai is also the first Maronite Cardinal Patriarch ever to participate in a papal conclave.