Spartathlon is a 246-kilometer (153 mi) ultramarathon race held annually in Greece since 1983, between Athens and Sparti, the modern town on the site of ancient Sparta. Five Royal Air Force officers attempted the course in 1982 and the competition was started the next year. The winner of the first Spartathlon, Yiannis Kouros, still holds the record for the fastest time at 20 hours and 25 minutes.

The Spartathlon aims to trace the footsteps of Pheidippides, an Athenian messenger sent to Sparta in 490 BC to seek help against the Persians in the Battle of Marathon. Pheidippides, according to an account by the Greek historian Herodotus, arrived in Sparta the day after he departed. Herodotus wrote: "On the occasion of which we speak when Pheidippides was sent by the Athenian generals, and, according to his own account, saw Pan on his journey, he reached Sparta on the very next day after quitting the city of Athens."

The Spartathlon is usually held around late September. Runners have 36 hours to run 246 km (153 mi), roughly the equivalent of six consecutive marathons, between Athens and Sparta. Runners have to deal with the Greek heat in the day, the cold of the night, and the mountainous terrain. There are 75 checkpoints along the way, where runners are disqualified for safety reasons if they fail to meet time cut-offs.

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