The CB class was a group of midget submarines built for the Italian Navy during World War II.

Power plant consisted of one Isotta Fraschini diesel engine and one Brown Boveri electric motor, both generating a total of 97 kilowatts (130 hp) powering a single shaft, resulting in a surfaced top speed of 7.5 knots (13.9 km/h; 8.6 mph) and a submerged top speed of 7 knots (13 km/h; 8.1 mph).

[3][4] The first six boats, completed in 1941, were transferred to the Black Sea by rail, after Nazi Germany asked for Italian naval support on the Eastern Front.

[5][6][7][8] After the Allied armistice with Italy in September 1943, the five Black Sea submarines (CB-1, CB-2, CB-3, CB-4 and CB-6) were transferred to the Royal Romanian Navy.

[14] The first six boats were unsuccessfully employed as submarine hunters near Naples and Salerno, before being transferred to the Black Sea in early 1942.

All of them, except CB-7 (later cannibalized for spare parts), remained in the italian navy when Italy joined the Allies.