Cause of death: pleurisy
Rodolfo Pietro Filiberto Raffaello Guglielmi di Valentina d'Antonguella (May 6, 1895 – August 23, 1926), known professionally as Rudolph Valentino and nicknamed The Latin Lover, was an Italian actor based in the United States who starred in several well-known silent films including The Four Horsemen of the Apocalypse, The Sheik, Blood and Sand, The Eagle, and The Son of the Sheik.
Valentino was a sex symbol of the 1920s, known in Hollywood as the "Latin Lover" (a title invented for him by Hollywood moguls), the "Great Lover", or simply Valentino. His early death at the age of 31 caused mass hysteria among his fans, further cementing his place in early cinematic history as a cultural film icon.
Source : Wikipedia