Sebastiano Martinelli (20 August 1848 – 4 July 1918) was a Cardinal of the Roman Catholic Church who served as Prefect of the Congregation of Rites.

He joined the Order of the Hermits of Saint Augustine (Augustinians) on 6 December 1863 and was professed on 6 January 1865.

[2] He was appointed apostolic delegate to the United States on 18 April 1896 by Pope Leo XIII and titular archbishop of Ephesus on 18 August 1896.

[4] He was created and proclaimed Cardinal-Priest of Sant'Agostino by Pope Leo XIII on 15 April 1901,[1] and received the red hat on 9 June 1902.

[1] He was a member of the commission, headed by Cardinal Pietro Gasparri, for the codification of canon law (1906–1917).

He is a small man, not over 5 feet 5 inches in height, of good build, and he has a typical Italian face.