Although no race in the ancient Greek Olympics was longer than 4,800 metres (3 miles), the marathon was the centrepiece event at the first modern Olympics, in part because of the legend of Pheidippides, who was said to have collapsed and died after running from Marathon to Athens with news of the Greek victory over the Persians at the Battle of Marathon (Marathon, Battle of) in 490 BC.

Louis's background is in dispute, but he may have been a shepherd who served in the Greek army. He was one of as many as 25 men who entered the marathon at the 1896 Games. About 30 km (20 miles) into the race, he took the lead. He finished in 2 h 58 min 50 sec, winning by more than seven minutes. As Louis entered the Panathenaic Stadium for his final lap, he was met by a thundering ovation; the Greek prince George and crown prince Constantine joined Louis on the final lap.

Louis's victory brought him immense popularity—the phrase egine Louis (“became Louis”) grew to be a common Greek phrase meaning “ran quickly”—and he became a symbolic representative of the modern Olympics, offering Adolf Hitler an olive branch at the start of the 1936 Games in Berlin.