The German Type IXB submarine was a sub-class of the German Type IX submarine built for Nazi Germany's Kriegsmarine between 1938 and 1940. The U-boats themselves were designed to be fairly large ocean-going submarines. The inspiration for the Type IXB submarine came from the earlier original Type IX submarine, the Type IXA submarine. The design of the IXA was developed to give an increased range, a change which resulted in a slightly heavier overall tonnage. This design was improved even further in the later Type IXC submarines.

German submarine U-110 was a Type IXB U-boat of Nazi Germany's Kriegsmarine that operated during World War II. She was captured by the Royal Navy on 9 May 1941 and provided a number of secret cipher documents to the British. U-110's capture, later given the code name "Operation Primrose", was one of the biggest secrets of the war, remaining so for seven months. President Franklin D. Roosevelt was only told of the capture by Winston Churchill in January 1942.