Stadion or stade (Ancient Greek: στάδιον) was an ancient running event, part of the Olympic Games and the other Panhellenic Games. It was one of the five major Pentathlon events. It was the premier event of the gymnikos agon (nude competitions). From the years 776 to 724 BC, the stadion was the only event that took place at the Olympic Games and the victor gave his name to the entire four-year Olympiad. This allows scholars to know the names of nearly every ancient Olympic Stadion winner.

The stadion was named after the building in which it took place, also called the stadion. This word became stadium in Latin, which became the English word stadium. There were other types of running events, but the stadion was the most prestigious; the winner was often considered to be the winner of an entire Games. Though a separate event, the stadion was also part of the ancient Pentathlon.

At the Olympic Games, the Stadion (the actual building) was big enough for twenty competitors, and the race was a 200-yard (about 180-meter) sprint. The original stadion track in Olympia measures approximately 190 meters. The race began with a trumpet blow, with officials (the agonothetai - ἀγωνοθέται) at the starting blocks to make sure there were no false starts. There were also officials at the end to decide on a winner and to make sure no one had cheated. If the officials decided there was a tie, the race would be re-run. Runners started the race from a standing position, probably with their arms stretched out in front of them, instead of starting in a crouch like modern runners. They ran naked on a packed earth track. By the fifth century, the track was marked by a stone-starting line known as the balbis. Advancements in this stone starting block led to it having a set of double grooves (10–12 cm apart) in which the runner placed his toes. The design of these grooves were intended to give the runner leverage for his start.