"Reckoner" is a song by the English alternative rock band Radiohead from their 2007 album In Rainbows. It was released as the album's fourth single on 23 September 2008. It was named one of the best songs of the decade by Pitchfork and the NME. Remixes of the song were released by electronic musicians James Holden, Flying Lotus and Diplo. Radiohead also released the separate stems for fans to remix themselves, as they had they done with their previous single "Nude".

On tour in 2001, Radiohead performed a different, aggressive song with the title "Reckoner" in George, Washington. During a solo performance at a 2005 Trade Justice Movement show, Radiohead singer Thom Yorke performed this version of "Reckoner" on acoustic guitar.

Working on the song for their 2007 album In Rainbows, Radiohead added a coda which developed into a new song, the version of "Reckoner" that appears on the album. In 2009, Yorke released the song originally known as "Reckoner" as a solo single, retitled "Feeling Pulled Apart by Horses".

"Reckoner" features "frosty, clanging" percussion, a "meandering" guitar line, piano, a string arrangement by Radiohead guitarist Jonny Greenwood, and Yorke's falsetto. Yorke said the guitar riff was a homage to Red Hot Chili Peppers guitarist John Frusciante, "in my sort of clunky 'can't-really-pick' kind of way".

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