Rear-Admiral Sir Thomas Louis, 1st Baronet was an officer of the Royal Navy who saw action during the American Revolutionary War and the French Revolutionary Wars. He was one of Horatio Nelson's "Band of Brothers" in the Mediterranean in 1798, commanding a ship at the Battle of the Nile. Later, he was second in command at the Battle of San Domingo, for which service he was made a baronet.

The Battle of the Nile was a major naval battle fought between the British Royal Navy and the Navy of the French Republic at Aboukir Bay on the Mediterranean coast off the Nile Delta of Egypt from the 1st to the 3rd of August 1798. The battle was the climax of a naval campaign that had raged across the Mediterranean during the previous three months, as a large French convoy sailed from Toulon to Alexandria carrying an expeditionary force under General Napoleon Bonaparte. The British fleet was led in the battle by Rear-Admiral Sir Horatio Nelson; they decisively defeated the French under Vice-Admiral François-Paul Brueys d'Aigalliers.