Rainiero d'Elci (7 March 1670 – 22 June 1761) was an Italian Cardinal.
He was born in Florence and was ordained in 1699. He entered papal service in the following year and held several offices both in Roman Curia and in the papal territorial administration. He was Inquisitor of Malta from 1711 until 1716.
He was consecrated titular archbishop of Rodi at the end of 1730. He served as apostolic nuncio in France 1731–1738. Pope Clement XII created him Cardinal on 20 December 1737 but did not publish it before the following June. In the same year he became archbishop of Ferrara, an office he held until 1740; he was then legate in that city.
He became bishop of Sabina (10 April 1747), then bishop of Porto e Santa Rufina (9 April 1753). He became Dean of the Sacred College of Cardinals at the death of Pietro Luigi Carafa on 15 December 1755, and as such he was transferred to the see of Ostia e Velletri (proper of the Dean) on 12 January 1756.