German submarine U-176 was a Type IXC U-boat in Nazi Germany's Kriegsmarine during World War II.

Built at the DeSchiMAG AG Weser shipyard in Bremen, she was laid down on 6 February 1941, launched on 12 September and commissioned on 15 December, under the command of Kapitänleutnant Reiner Dierksen.

U-176 completed three patrols, sinking 11 ships totalling 53,307 gross register tons (GRT) before she was sunk off Cayo Blanquizal by the Cuban Navy on 15 May 1943.

The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of 4,400 metric horsepower (3,240 kW; 4,340 shp) for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1,000 shaft horsepower (1,010 PS; 750 kW) for use while submerged.

On 27 November she sank the 5,922 GRT Dutch merchant ship Polydorus after a 50-hour pursuit, the longest recorded by any U-boat in the Second World War.

At 17:15 hours, a U.S. Navy Kingfisher aircraft from squadron VS-62 operating from Cuba spotted U-176 at 23°21′N 80°18′W / 23.350°N 80.300°W / 23.350; -80.300 and dropped a smoke float to mark her position about one and a half miles astern of the convoy.

Rear Admiral Samuel E. Morison, official historian of the US Navy, recognized his success in his work History of United States Naval Operations in World War II, where he also praised the ability and efficiency of the Cuban seamen.

[21] The CS-13 patrol boat, commanded by Second Lieutenant Mario Ramirez Delgado, turned toward the gas, made good contact through the sonar and launched two perfect attacks with deep charges which annihilated the U-176.

This was the only successful attack against a submarine carried out by a surface unit smaller than a PCE [Patrol Craft Escort] of 180 feet.