The London-born singer's sophomore record - which was recently named as the UK's biggest-selling album of the 21st century with over 3.8m copies to date - returned for a third stint in pole position in its 50th week of release.
21 has now become the longest-running number one album for almost 42 years and achieved the sixth-greatest reign in history, finishing behind releases from music legends The Beatles and Simon & Garfunkel.
Adele is trailed by fellow chart veteran Doo Wops & Hooligans by Bruno Mars, a non-mover at two, and last week's number one + by Ed Sheeran at three.
New mother Beyoncé celebrates by seeing her 4 album leap from 12 to six in its 28th week of release, while Olly Murs drops three to seven with In Case You Didn't Know and Jessie J's Who You Are scrambles two to eight.
Rihanna falls three to round out the Top 10 with Talk That Talk, as Westlife's Greatest Hits album and Will Young's Echoes move in the opposite direction, climbing two and four respectively to 11 and 12.
One Direction slip back to the double digits after falling six to 14 with Up All Night, the self-titled debut from Noel Gallagher's High Flying Birds is up three to 15 and The Vaccines manage a mighty shift from 33 to 16 with What Did You Expect From The Vaccines.
Adele's 21 success is complemented by the return of its predecessor 19 to the upper half of the top 40. The January 2008 release rises 22 places to 18 and is trailed by Florence + The Machine's Ceremonials at 19 and The Lady Killer by Cee Lo Green at 20.
The Top 10 in full:
1. (6) Adele: '21'
2. (2) Bruno Mars: 'Doo Wops & Hooligans'
3. (1) Ed Sheeran: '+'
4. (3) Coldplay: 'Mylo Xyloto'
5. (5) Amy Winehouse: 'Lioness: Hidden Treasures'
6. (12) Beyonce: '4'
7. (4) Olly Murs: 'In Case You Didn't Know'
8. (10) Jessie J: 'Who You Are'
9. (9) Rebecca Ferguson: 'Heaven'
10. (7) Rihanna: 'Talk That Talk'
Source: Official Charts Company
> This week's singles chart
Watch the video for 'Someone Like You' from Adele's number one album 21 below:
View the latest Official Top 100 Album Chart