Prospero Colonna, Duke of Rignano, Prince of Sonnino (18 July 1858 – 16 September 1937) was an Italian politician and aristocrat.

Prospero was born in Naples, son of Giovanni Andrea I Colonna, a landowner, and Isabella Alvarez di Toledo.

During his term, Rome completed a streetcar line, including a passage under the Quirinal Hill.

[1] In June 1904 the IOC's President Pierre de Coubertin chose Rome as the host for the IV Olympic Games, but Colonna refused due to the difficult status of the city treasury.

[2] When the First World War started, Colonna joined in the Italian Royal Army as cavalry colonel.