"21 Seconds" is a song by UK garage group So Solid Crew. Released as the second single from their 2001 debut album They Don't Know, it was the first of five consecutive top-20 hit singles for the group.

The song uses fairly stripped back production, utilising a 2-step rhythm which was common in UK garage at the time. Lisa Maffia's young daughter, Chelsea, can be heard at the beginning of the track, saying "Ha, ha, ha, whatcha laughin at?"^[2]

The song title alludes to the approximate 21 seconds that each of the band members is given to perform their rap. 21 seconds is arrived at as the song's tempo is approximately 140BPM, has a key of G minor, and each rapper has 12 bars of 4 beats (48 beats at 140BPM, when worked out to the nearest integer, rounds to 21 seconds).^[2] Megaman said the crew created the track after their label told them to make a track lasting three and a half minutes. He said "so we worked out that with at least 10 or 11 members, that's eight bars each – 21 seconds. It was a simple calculation."^[3] Their label manager Shabs Jobanputra said "they literally took a calculator and divided the time by the number of MCs."^[4]

The music video for "21 Seconds" was directed by Max Giwa and Dania Pasquini and was released on 2001. It features members from So Solid Crew performing during the storm in front of fences full of people dancing. It heavily uses special effects such as the storm, clouds, helicopters, lightning, tornado, etc.

The music video received the award for British Video of the Year at the 2002 Brit Awards.^[5]

In a 2002 review, Pete Paphides in The Guardian said the track was "a brilliant idea" but that "not a single member of the collective uses their time to say anything remotely insightful."^[6] In September 2019, NME included the song in their "25 essential UK garage anthems" list.^[7] In a 2020 retrospective review of the single, The Quietus said the track "managed to capture the excitement of clubs and pirate radio, with MCs frantically passing the mic as they try to outdo each other in lyrical prowess, creative aggression bubbling beneath the surface."^[8] The same year, The Guardian placed the song at number 48 on their list of "The 100 Greatest UK No 1 Singles".^[9]

"21 Seconds" reached number one on the UK Singles Chart in August 2001, selling 118,135 copies in its opening week^[10] and becoming 2001's 19th best-selling single. Its total sales reached 423,000. The single also peaked at number 24 in Ireland.

Romeo reworked "21 Seconds" for car insurance firm Confused.com in 2013.^[28] The same year, Preditah reworked the track.^[29] On 6 September 2019, So Solid Crew went to the Red Bull Music Studios, London, and remixed "21 Seconds" with Toddla T.^[30] They were joined by D Double E, Ms Banks and DJ Q as they added new verses.