Giovanni Simeoni (July 12, 1816 – January 14, 1892) was an Italian Cardinal of the Roman Catholic Church who served as Prefect of the Sacred Congregation for Propagation of the Faith from 1878 until his death, and was elevated to the cardinalate in 1875.
Giovanni Simeoni was born in Paliano; his father was a majordomo of the Colonna family. He attended the seminary in Palestrina before going to Rome to study at the Collegio Romano and La Sapienza University, where he studied theology and canon law. The Colonna family subsidized his studies.
Simeoni was ordained to the priesthood in 1839. He then served as preceptor of the children of Prince Colonna, and as professor of philosophy and theology at the Pontifical Urban Athenaeum of Propaganda Fide. After being raised to the rank of Privy Chamberlain of His Holiness, he was made auditor of the nunciature to Spain and Domestic Prelate of His Holiness (1857). Simeoni later became adiutor ab actis of the Sacred Congregation for the Propagation of the Faith, and served as the Congregation's secretary from 1868 to 1875.