The Megalesia or Megalenses Ludi is an ancient Roman festival in honor of the Magna Mater (great mother) Cybele that lasted for six days, beginning on April 4th.
It celebrated the bringing of Cybele’s sacred relic from Pessinus to Rome and the dedication of Her temple by Marcus Junium Brutus in 203 BC. The statue was brought to Rome during the Punic Wars because the Sibylline Books predicted that the Phrygian Goddess would help them defeat Hannibal.
The Megalesia was celebrated with processions, feasting, games, and plays.
Cybele’s festivals in Phrygia included self-mutilation, but this sort of activity was not likely to be appealing to the Roman people and was probably restricted to the priests. The populous at large preferred the party.