The Olympic games were the eldest and most important games of the periodos, held in honour of Zeus. They were founded in 776 BC and were held at Olympia, a sanctuary in the western Peloponnesos, in the area of Pisa. Originally the games were probably organized by this small town, but from about 570 BC onwards, the games were definitely under the control of the bigger city Elis, about 50 km north of Olympia. In this city were more men and more money available for the extensive organization. The games lasted for more than a millennium and came to their end in the early fifth century AD.

The games were held every four years in the summer. The period of four years, starting with the year of the games, was called an olympiad. The games had a duration of only five days, but the athletes had to come to Elis near Olympia one month in advance for the training under the control of the hellanodikai.

In the program of the games, the accent lay on athletics, although there were also horse races. Musical events were absent at the Olympic games, except for the contests for heralds and trumpeters. The prize for the winners was an olive crown. For women separate games were organized, the Heraia.

The Olympic games attracted thousands of spectators. They had a great influence on all other games. From 300 BC onwards, is-Olympic games were held in the whole Greek world. The games remained popular in the Roman period, until the end of the fourth century. In 1896 the first modern Olympics were held, for practical reasons not at Olympia, but in Athens.