The Pisani-class submarines were built for the (Royal Italian Navy) during the late 1920s. They played a minor role in the Spanish Civil War of 1936âÂÂ1939 supporting the Spanish Nationalists.
Designed in parallel with the s, the Pisani class was larger to accommodate more fuel and give them more range. They displaced surfaced and submerged. The submarines were long, had a beam of and a draft of . They had an operational diving depth of . Their crew numbered 48 officers and enlisted men.
For surface running, the boats were powered by two diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a electric motor. Like the Mamelis, their stability was poor and they had to be modified with bulges after completion. This reduced their speeds from on the surface and underwater to and respectively. On the surface, the Pisani class had a range of at ; submerged, they had a range of at .
The boats were armed with six torpedo tubes, four in the bow and two in the stern for which they carried a total of nine torpedoes. They were also armed with a single deck gun forward of the conning tower for combat on the surface. Their anti-aircraft armament consisted of two machine guns.
During the Spanish Civil War, Vettore Pisani made at least one patrol off the Catalan coast in August 1937 during which she made one unsuccessful attack.