German submarine U-106 was a Type IXB U-boat of Nazi Germany's Kriegsmarine that operated during World War II.

She was laid down on 26 November 1939 at DeSchiMAG AG Weser in Bremen as yard number 969, launched on 17 June 1940 and commissioned on 24 September.

U-106 helped to catalyze Mexico's entry into World War II on the side of the Allies by sinking one of two oil tankers; the Faja de Oro.

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 metric horsepower (740 kW; 990 shp) for use while submerged.

She sank seven more ships and damaged two others, including the battleship HMS Malaya in the vicinity of Senegal and the Cape Verde Islands.

[3]: 100–105 Any success on the boat's fourth sally was marred on 23 October 1941 by the discovery that an entire watch, (four men), had been washed overboard in heavy seas on the western edge of the Bay of Biscay.

For her fifth patrol, U-106 sailed along the eastern coast of the United States and sank five ships, during the so-called "Second Happy Time".

Patrol number six also benefitted from a change of operational area to the Gulf of Mexico, where the boat sank five more ships and damaged a sixth.

One of them, the tanker Faja de Oro, on 21 May 1942, was the second ship to be sunk which helped to facilitate Mexico's declaration of war on Germany on 1 June.

The first watch officer (1WO) was killed; the commander was wounded, forcing the boat to put about, returning to Lorient on the 29th, just five days after setting out.

The U-boat's 10th and final patrol began on 28 July 1943; she was sunk on 2 August of that year off northern Spain, after being damaged by a Wellington of No.