Ettore Fieramosca was an Italian submarine which served with the Regia Marina in World War II.

Due to her huge cost and these shortcomings, plans to build more boats to the same designs were shelved.

During the Spanish Civil War, she unsuccessfully attacked the Republican light cruiser Méndez Núñez and the destroyers Sánchez Barcáiztegui and Gravina with three torpedoes on a patrol from 21 December 1936 to 5 January 1937.

[3] Plagued with incidents and mechanical trouble for her entire career, she was deployed on only a few operational patrols in 1940, but did not achieve any successes against enemy targets.

She suffered a battery explosion late in 1940 and was decommissioned in April 1941; eventually she was stricken and scrapped.