Horatio Nelson (September 29, 1758 – October 21, 1805) was a Human who lived on Earth during the 18th and 19th centuries. A citizen of the United Kingdom, he began a career in the Royal Navy at the age of 12, and rose to become one of the most famous Admirals in British naval history.
Under Nelson's command, a British force defeated a larger combined French/Spanish force in the Battle of Trafalgar, however he died during the course of the battle on the deck of his ship, the HMS Victory. Centuries later, Starfleet Captain Jean-Luc Picard would recall to Guinan the tradition of captain's touring their ships just before a major battle. She replied that it was usually done before a hopeless battle, and Captain Picard offered Nelson touring his ship just before Trafalgar as an example of a battle that was won after the Captain toured the ship. Guinan recalled that Nelson had died in the battle. (TNG episode: "The Best of Both Worlds, Part I")
Starfleet later honored Nelson's flagship by commissioning the Constellation-class USS Victory. Lieutenant Geordi La Forge once built a scale model of the HMS Victory as a gift for Captain Zimbata. (TNG episode: "Elementary, Dear Data")
In 2277, Kirk compared meeting Starfleet Fleet Admiral Karis Tatenen to meeting Nelson or Francis Drake. Later on, Kirk compared Tatenen's story of the Battle of Vonra to be a kin to how Nelson might have spoke about the Battle of Trafalgar. (TOS - Star Trek II Short Stories short story: "The Blaze of Glory")
When Admiral William Ross wished him good luck prior to the Battle of Cardassia, Captain Sisko recalled Admiral Nelson's words before the Battle of Trafalgar. (DS9 novelization: What You Leave Behind)