Leonardo Antonelli (6 November 1730 – 23 January 1811) was an Italian Cardinal in the Roman Catholic Church. A native of Senigallia, Antonelli was the nephew of Cardinal Nicolò Maria Antonelli. During the early part of his long diplomatic career, he held, among other offices, those of canon of the Vatican Basilica, Prefect of archives in the Castle of San Angelo, Secretary of the Sacred College and Assessor of the Holy Office. 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.