Oxegen '08 was the fifth Oxegen festival to take place, following the dissolution of its predecessor Witnness in 2004. It took place on the weekend of Friday 11 July, Saturday 12 July and Sunday 13 July at Punchestown Racecourse near Naas in County Kildare, Ireland. For the first time the festival was a three-day event. The festival was headlined by Kings of Leon on the Friday, The Verve and R.E.M. on the Saturday and Rage Against the Machine on the Sunday.

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.