Mario Guaita, also known by the pseudonym Mario Ausonia (1881 – 1956), was an Italian actor and director.

Guaita studied medicine and stopped his studies due to his hobby of powerlifting. He began performing in the theater with circus and vaudeville shows in Europe and America. In cinema he played strongman and acrobat roles for Pasquali Film and later for Gloria Film.

His greatest successes in action and adventure films are The Phantom Athlete (1919), Battle of the Giants (1919), Atlas (1920), The Amazon Belt (1920), The Billion Ship (1922) and The Pearl Fisherman (1923), of which he was also partly director. He made fifteen films with his screenwriter wife Renée Deliot in Italy and France, where they moved during the depression years of the Italian film industry in the early 1920s. Guaita's last film was in 1926 with Executioner in the Land of Gold. Subsequently he ran a cinema in Marseille.