Music
The influential Mike Patton-fronted metal band had recently confirmed a reunion for a number of European shows after their 1998 split.
Organisers said the performance at Download would be the band's only UK live gig during 2009.
A band statement read: "[We are] still young and strong enough to deliver a kickass set, with enthusiasm to not only revisit our past but possibly add something to the present.
"And so with this we've decided to hold our collective breaths and jump off this cliff....Back, God forbid, into the monkey cage!!!"
Live Nation executive Andy Copping compared the band's return to "the second coming of Christ" and Kerrang! editor Paul Brannigan said he "couldn't be more thrilled" at the news.
Faith No More join Def Leppard and Slipknot in headlining this year's Download festival, which will also see performances from Mötley Crüe, The Prodigy, Korn and others.
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