HMS Lion was a 80-gun second rate Vanguard-class ship of the line built for the Royal Navy in the 1840s.

In 1871 Lion was converted into a training ship at HM Dockyard, Devonport.

The Vanguard class was designed by Sir William Symonds, Surveyor of the Navy, with each ship built with a slightly different hull shape to evaluate their speed and handling characteristics.

[2] The Vanguard class ships of the line were armed with twenty 32-pounder (56 cwt)[Note 1] cannon and two 68-pounder carronades on her lower gundeck, twenty-eight 32-pounder (50 cwt) cannon and another pair of 68-pounder carronades on the upper gundeck.

On trials the engine produced 1,665 indicated horsepower (1,242 kW) which gave the ship a speed of 10.4 knots (19.3 km/h; 12.0 mph).