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 inches (45.0 cm) in diameter, beginning with the "Fiume" Whitehead torpedo of 1890.

First introduced into British service in 1894.^[1]

• Year : about 1888
• Weight : 845 lb (383 kg)
• Length : 11 ft 8 in (3.56 m)
• Warhead : 118 lb (54 kg) wet gun-cotton
• Performance : 26.5 knots (49.1 km/h; 30.5 mph) for 800 yd (730 m)
• Propulsion : Compressed air

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

• Year : about 1899^[1]
• Weight : 1,353 lb (614 kg)
• Warhead : 296 lb (134 kg) including pistol
• Propulsion : Compressed air

Used on destroyers of the early 1900s.

• Year : about 1904^[1]
• Performance : 28.5 knots (52.8 km/h; 32.8 mph) for 4,000 yd (3,700 m) or 41 knots (76 km/h; 47 mph) for 1,000 yd (910 m)
• Propulsion : Compressed air

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.

• Year : 1907^[1]
• Warhead : 320 lb (150 kg) TNT
• Performance :
  • Mark VII :
    30 knots (56 km/h; 35 mph) for 6,000–7,000 yd (5,500–6,400 m)
    41 knots (76 km/h; 47 mph) for 3,000 yd (2,700 m)
  • Mark VII* :
    29 knots (54 km/h; 33 mph) for 7,000 yd (6,400 m)
    35 knots (65 km/h; 40 mph) for 5,000 yd (4,600 m)
• Propulsion : Wet-heater

• Year: 1913
• Role: Submarines and aircraft (Note: During World War II and after the Mk.VIII was a 21-inch torpedo)
• Warhead: 320 lb (150 kg) TNT
• Propulsion: Wet heater
• Performance: 35 knots (65 km/h; 40 mph) for 2,500 yd (2,300 m)

• Year: 1934
• Aircraft carried
• Dimensions: 17.72 in (450 mm) dia.
• Warhead: 465 lb (211 kg) TNT
• Propulsion: Burner cycle
• Performance: 35 knots (65 km/h; 40 mph) for 2,500 yd (2,300 m)

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

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

• Year: 1942
• Operators: Fleet Air Arm, RAF Coastal Command, Royal Navy
• Role: Aircraft and Motor Torpedo Boats, 1943 onwards
• Dimensions: 17.69 in (449 mm) × 17 ft 2.7 in (5.250 m)
• Warhead: 545 lb (247 kg) Torpex
• Propulsion: Burner cycle
• Performance: 40 knots (74 km/h; 46 mph) for 2,500 yd (2,300 m) or 33 knots (61 km/h; 38 mph) for 3,200 yd (2,900 m)^[2]

Electric torpedo project not completed.

• United Kingdom, 1944
• Aircraft launched
• Operated by FAA, RAF Coastal Command, Blackburn Firebrand
• Dimensions: 17.72 in (450 mm) × 17 ft 3 in (5.26 m)
• Warhead: 600 lb (270 kg) Torpex
• Propulsion: Burner cycle
• Performance: 40 knots (74 km/h; 46 mph) for 2,500 yd (2,300 m)

An air-dropped passive acoustic homing torpedo known as "Dealer" and "Dealer B".^[3]

• Length: 8 ft (2.4 m)^[4]
• Weight: 646 lb (293 kg)
• Performance: 12.5 knots (23.2 km/h; 14.4 mph) for 3,000 yd (2,700 m) or 19 knots (35 km/h; 22 mph) for 830 yd (760 m)

• British 21-inch torpedo
• List of torpedoes