Isthmian Games or Isthmia (Ancient Greek: Ἴσθμια) were one of the Panhellenic Games of Ancient Greece, and were named after the Isthmus of Corinth, where they were held. As with the Nemean Games, the Isthmian Games were held both the year before and the year after the Olympic Games (the second and fourth years of an Olympiad), while the Pythian Games were held in the third year of the Olympiad cycle.
The Games were reputed to have originated as funeral games for Melicertes (also known as Palaemon), instituted by Sisyphus, legendary founder and king of Corinth, who discovered the dead body and buried it subsequently on the Isthmus. In Roman times, Melicertes was worshipped in the region.
Theseus, legendary king of Athens, expanded Melicertes' funeral games from a closed nightly rite into fully-fledged athletic-games event which was dedicated to Poseidon, open to all Greeks, and was at a suitable level of advancement and popularity to rival those in Olympia, which were founded by Heracles. Theseus arranged with the Corinthians for any Athenian visitors to the Isthmian games to be granted the privilege of front seats (prohedria, Ancient Greek προεδρία). Another version states that Kypselos, tyrant of Corinth in the 7th century BC, returned to the Games their old splendour.
If we are to accept the traditional date of the first Olympic Games (776 BC), we can say that the first Isthmian Games would have been held in 582 BC.