Mario Gaioni, also written as Mario Gajoni, (20 November 1880 – 9 December 1946) was an Italian professional road racing cyclist during the 1900s and early 1910s. He won the Erba–Lurago–Erba race in 1905, set a record for the "Giro d'Italia" in 1907 and finished 14th overall in the 1909 Tour de France.