SM U-166
 SM U-166 was one of the 329 submarines serving in the Imperial German Navy. She was a Type Mittel U submarine launched in 1918. She was engaged in the naval warfare of World War I and took part in the First Battle of the Atlantic. She surrendered on 21 March 1919 and became the French submarine Jean Roulier until 24 July 1935. U-166 was broken up.