HMS Agamemnon was a Royal Navy 91-gun battleship ordered by the Admiralty in 1849, in response to the perceived threat from France by their possession of ships of the Napoléon class.

She therefore carried a full square rig on three masts, in common with large sailing warships of the period.

[3] She was named after Agamemnon, the King of Mycenae, who led the Greek forces in the Trojan War.

She carried an armament of muzzle loading smooth-bore cannon, typical of warships at this time, on two decks.

[3] Agamemnon was attached to the Mediterranean Fleet and served in the Crimean War as flagship of Rear-Admiral Sir Edmund Lyons.