Mittel U was a class of U-boats built during World War I by the Kaiserliche Marine.

Mittel U U-boats carried 16 torpedoes and had various arrangements of deck guns. Some had only one 88mm gun while others had a single 105mm gun - but most had both originally. In 1917 some of the boats were refitted with a single 105mm gun.

They carried a crew of 39 and had excellent seagoing abilities with a cruising range of around 11,220 miles. Many arrangements from the Mittel U were also seen on the World War II Type IX U-boats when their design work took place 20 years later.

Between 1915 and 1919 46 were built, amongst them U-88 with Walther Schwieger as commander and U-103 with Claus Rücker.