The Type UC I coastal submarines were a class of small minelaying U-boats built in Germany during the early part of World War I. They were the first operational minelaying submarines in the world. A total of fifteen boats were built. The class is sometimes also referred to as the UC-1 class after SM UC-1, the class leader. The Italian X-class submarine was a reverse-engineered and modified type of the UC-1-class.

SM UC-1 was a German Type UC I minelayer submarine or U-boat in the German Imperial Navy during World War I. The U-boat had been ordered by November 1914 and was launched on 26 April 1915. She was commissioned into the German Imperial Navy on 5 July 1915 as SM UC-1. Mines laid by UC-1 in her 80 patrols were credited with sinking 41 ships. UC-1 disappeared after 18 July 1917. UC-1 was sunk on 24 July 1917 by F2B Felixstowe flying boat. Standard practice was to fly along the U boat and drop 2 250lb bombs astride it, hoping to cause leaks and give time for a destroyer to collect the submariners and sink it. On this occasion, by fluke, one bomb went through the conning tower and blew the base out of UC1. MFG Mill was awarded the DFC for this but he refused to wear it because of the total loss of life <london Gazette> <MFG Mill Diaries>