She initially had 24, 18 and 8 pounder guns spread over her lower, upper, quarter and forecastle decks, but by 1805 she carried 36-pounders instead of 24-pounders.

Her original crew was 21 officers and 642 ratings and soldiers, though it was 956 at the Battle of Cape Finisterre and 800 at Trafalgar.

A sister ship of the Neptuno, she was ordered in November 1795 and launched in June 1798 in Ferrol, to the design of Julian Martín Retamosa.

On the 21 October the same year she was present in Federico Gravina's second squadron at the Battle of Trafalgar, under the command of Captain Antonio Pareja and his deputy, Frigate Captain Pedro Albarracin, and losing 60 dead and 148 wounded.

On 24 October HMS Defiance rescued survivors from the Argonauta and made a failed attempt to re-establish a tow.