There have been a number of 18-inch (45cm) torpedoes in service with the Royal Navy of the United Kingdom. These have been used on ships of the Royal Navy and aircraft of both the Fleet Air Arm and Royal Air Force, while Royal Navy surface ships and submarines use 21-inch torpedoes. The British 18-inch torpedoes were 17.72 in in diameter, beginning with the "Fiume" Whitehead torpedo of 1890.

45 cm "Fiume" (Whitehead) torpedo

First introduced into British service in 1894.

Mark V

Used on the River-class and 1905 Tribal-class destroyers.

Mark VI

Used on destroyers of the early 1900s.

Mark VII and VII*

Introduced on the 1908 members of the 1905 Tribal class destroyers. Used by torpedo boats built before the First World War and destroyers. Used by RAF flying boats in the 1920s. 30 kn for 6000 - 7000 yd 41 kn for 3000 yd 29 kn for 7000 yd 35 kn for 5000 yd

Mark VIII

Mark XI

Mark XII

Aircraft launched, used by Fleet Air Arm and RAF Coastal Command.

Mark XIV

The Mark XIV was an aircraft-launched torpedo. Stocks were lost with the fall of Singapore.

Mark XV

Mark XVI

Electric torpedo project not completed.

Mark XVII

Mark 30

An air-dropped passive acoustic homing torpedo known as "Dealer" and "Dealer B".