The first U-19 was the lead ship of her type. Her construction was ordered on November 25, 1910, and her keel was laid down on October 20, 1911, at the Kaiserliche Werft of Danzig. She was launched on October 10, 1912, and commissioned into the Kaiserliche Marine on July 6, 1913.
From August 1, 1914, to March 15, 1916, U-19 was commanded by Constantin Kolbe. He was relieved by Raimund Weisbach, who had previously served as torpedo officer on U-20 and had (on Käpitanleutnant Schweiger's orders) launched the torpedo that sank Lusitania. During his brief command, Weisbach carried out an unusual mission: he delivered the revolutionary Roger Casement and two other agents to Ballyheige Bay in Ireland in hopes that they would foment an uprising that would distract the United Kingdom from World War I.
Weisbach was relieved on August 11, 1916, by Johannes Spieß, who was relieved in turn on June 1, 1917, by Heinrich Koch. Koch turned the boat over on October 25, 1917, to Hans Albrecht Liebeskind, who commanded for less than a month before being relieved on November 17, 1917, by Johannes Spieß again. On June 1, 1918, Hans Albrecht Liebeskind took over again and commanded U-19 until the end of the war.
U-19 conducted 12 patrols, sinking 46 ships totalling 64,816 tons, including Santa Maria (5,383 tons) off Lough Swilly on February 25, 1918, Tiberia (4,880 tons) off Black Head near Larne on February 26, 1918, and HMS Calgarian (17,500 tons) off Rathlin Island on March 1, 1918.
On November 11, 1918, U-19 was surrendered to the British, and was broken up at Blyth sometime in 1919 or 1920.
The second U-19 was a Type IIB submarine. Her keel was laid down on July 20, 1935 at the Germaniawerft of Kiel. She was launched on December 21, 1935, and commissioned into the Kriegsmarine on January 16, 1936, under the command of Käpitanleutant Viktor Schütze.
U-19 conducted 20 patrols, sinking 15 ships totalling 35,871 tons. On May 1, 1940, U-19 was withdrawn from combat duty and used for training and as a school boat. On May 1, 1942, she returned to active duty. On September 10, 1944, she was scuttled in the Black Sea off the coast of Turkey. U-19 suffered no casualties to any of her crews.