SM U-78 was one of the 329 submarines serving in the Imperial German Navy in World War I. U-78 was engaged in the naval warfare and took part in the First Battle of the Atlantic as a minelayer. On 27 October 1918 low frequency communications from U-78 in the Skagerrak were detected by the British submarine G2 which sank her with the loss of her crew of 40. The commonly listed sinking date of October 28, 1918 is in error.