"The National Anthem" is a song by the English rock band Radiohead, and the third track from their fourth studio album, Kid A. The song is moored to a repetitive bassline, has a processed electronic production and develops in a direction influenced by jazz. The song was written by Radiohead, who co-produced it with Nigel Godrich. It has been played frequently at Radiohead concerts since the release of Kid A in 2000. It received polarised reviews by critics.

An early demo of "The National Anthem" is included in the special edition of the 2017 OK Computer reissue, OK Computer OKNOTOK 1997 2017. Radiohead singer Thom Yorke wrote the song's bassline when he was 16, and played the bassline on the studio recording. In 1997, Radiohead recorded drums and bass for the song, intending to develop it for an OK Computer B-side, but decided to save it for their next album. Greenwood added ondes Martenot and sampled sounds from radio stations, and Yorke's vocals were processed with a ring modulator. The jazz musicians were conducted by Yorke and Radiohead multinstrumentalist Jonny Greenwood. Yorke said: "the running joke when we were in the studios was, 'Just blow. Just blow, just blow, just blow'".

The free jazz-style wind section featured in the song, influenced by jazz bassist and composer Charles Mingus, creates a soundscape of chaos, and has been described as "a brass band marching into a brick wall" by one reviewer.Simon Reynolds of Spin said: "the song is a strange, thrilling blast of kosmik highway music — combining Hawkwind's "Silver Machine" with Can's "Mother Sky" and throwing in free-jazz bedlam for good measure". Cam Lindsey of Exclaim! wrote that the song is a "radical jazz-rock fusion".

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