Medusa was born in August 2014 in Cullera, a seaside town south of Valencia, as an initiative by Valencian promoters. Its director, Andreu Piqueras, has said he chose the town for its potential as a music destination. The first line-up brought together DJ Nano, Cristian Varela, Fatima Hajji, DJ Marta and Christian Smith.
From 2015 the festival bet on scenery: an underwater mainstage some sixty metres wide, its DJ booth set in the mouth of a shark, by the fallas artist Fede Alonso. Atlantis followed in 2016, a jungle in 2017, an alien invasion in 2018 and the Queen's Castle in 2019. After two editions cancelled by the pandemic, the 2022 edition ended in mourning: overnight on 12 to 13 August, gusts of wind brought down structures, a 22-year-old festival-goer died and dozens were injured, and the organisers cancelled the rest.
Every edition has its theme, and the mainstage is rebuilt from scratch: Age of Times in 2023, The Dreams of Hathör for the tenth anniversary in 2024, Arcade Land and its pixelated castles in 2025, and APSARAS in 2026, a temple inspired by Angkor Wat about 105 m wide and 27 m high. Opening ceremonies there combine drones, pyrotechnics and video. According to its spokesperson in 2025, the festival's capital remains Valencian, in the hands of its two founding partners.
In 2026 the organisers reported 185,000 cumulative admissions over four days and a peak of 56,000 people at once on the Saturday, with 150 DJs. The crowd is mostly Spanish: in 2025, according to the organisers, nine in ten festival-goers were from Spain, with foreigners coming mainly from France. Medusa won best festival in Spain at the Vicious Music Awards in November 2025 and ranks 88th in DJ Mag's Top 100 Festivals in 2026, a reader-voted list.