SM UC-33 was a German Type UC II minelaying submarine or U-boat in the German Imperial Navy (German: Kaiserliche Marine) during World War I. The U-boat was ordered on 29 August 1915 and was launched on 26 August 1916. She was commissioned into the German Imperial Navy on 25 September 1916 as SM UC-33. In seven patrols UC-33 was credited with sinking 36 ships, either by torpedo or by mines laid. UC-33 was shelled and then rammed by patrol boat PC61 captained by Frank Worsley at position 51°55′N 6°14′W / 51.917°N 6.233°W in St. George's Channel on 26 September 1917.