Oxegen was a music festival in Ireland, first held from 2004–2011 as a rock and pop festival and again in 2013 with dance and chart acts only. The event was regularly cited as Ireland's biggest music festival, and, by 2009, it was being cited as the greenest festival, being a 100% carbon neutral event in Ireland, although this claim is highly disputed as green-washing. It was previously called Witnness, which ran from 2000 and was sponsored by Guinness. The event was promoted by MCD and was sponsored by Heineken. Oxegen was originally a three-day festival, but from 2008 onwards, it was expanded to four days.

Witnness was an Irish music festival, sponsored by Guinness, which ran for four consecutive summers from 2000 to 2003. Originally it was held at Fairyhouse Racecourse in County Meath, but it was moved to Punchestown Racecourse in County Kildare for its final year.