He was created Cardinal-priest of Santa Sabina by Pope Pius VI in the consistory of 24 April 1775, and later Dean of the Sacred College and Cardinal Bishop of Ostia-Velletri.
In addition to the responsible posts already mentioned, he filled those of grand penitentiary, prefect of the Signature of Justice and of the Congregation of the Index, and pro-secretary of Briefs.
[2] In 1808, he was banished from Rome by the French to Spoleto and later to Sinigaglia, where he died, leaving to the Congregation of Propaganda bequests for the support of twelve Armenian students in the College of Urbano.
Though Antonelli has been criticized for arrogating to the papacy too arbitrary a civil power, a perusal of his letter to the bishops of Ireland reveals a more tolerant spirit than is generally attributed to him.
Possessed of a rich library, he was the friend and protector of letters, and had as librarian, the learned Francesco Cancellieri.