San Juan Nepomuceno was a Spanish ship of the line launched in 1765 from the royal shipyard in Guarnizo (Cantabria). Like many 18th century Spanish warships she was named after a saint. She was a solidly built ship of proven seaworthy qualities. Captured by the British Royal Navy during the Battle of Trafalgar, the ship was renamed first HMS Berwick, then HMS San Juan. The ship was discarded in 1816.

The Battle of Trafalgar was a naval engagement that took place on 21 October 1805 between the British Royal Navy and the combined fleets of the French and Spanish Navies during the War of the Third Coalition of the Napoleonic Wars (1803–1815).