Domenico Mariani (3 April 1863 – 23 April 1939) was an Italian cardinal of the Roman Catholic Church who was President of the Administration of the Property of the Holy See from 1935 until his death, following eighteen years as secretary of that body.
He was educated at the Lyceum "Angelo Mai", Rome, and the Pontifical Roman Seminary there.
He was Canon of the Vatican Basilica until 1917 and was created Privy Chamberlain of His Holiness on 30 September 1914.
He served as Secretary of the Cardinalitial Commission for the Administration of the Properties of the Holy See from 1917.
He was created Cardinal-Deacon of S. Cesareo in Palatio in the consistory of 16 December 1935 by Pope Pius XI.