The 'Someone Like You' singer notched up a 17th Sunday at number one with her sophomore record, which was first released 25 weeks ago and has never finished lower than two on the rankings.
Adele's climb sends last week's chart victor 4 by Beyoncé into the runner-up spot, while Adele's 2008 debut 19 follows its successor up the digits to settle in at three.
The top five is rounded out by another former chart topper in the shape of Lady GaGa's Born This Way and a new entry from indie band The Horrors, entitled Skying.
Past number ones also fill four of the five remaining spots in the Top 10, with the biggest shake-ups belonging to Wasting Light by the Foo Fighters, up four to eight, and Take That's Progress, which is down to nine from last week's five.
Elsewhere, Cee Lo Green and Jessie J slip out from the biggest sellers with their LPs The Lady Killer and Who You Are, down three apiece to 12 and 13 respectively. Entering just one spot behind them are Nickelodeon boyband Big Time Rush, who score the week's second highest new entry with their debut album BTR.
Lower down the numbers sees two big re-entries from David Guetta's One Love, which is at 17 after 92 weeks on the chart, and Andrea Bocelli's best-of collection Vivere, propelled back to 19 in its 109th week of release by the tenor's performance on the Popstar to Operastar final last Sunday.
The top 20 is completed by the seventh studio album from US rockers Incubus If Not Now, When?, a brand new entry this week.
The Top 10 in full:
1. (2) Adele: '21'
2. (1) Beyoncé: '4'
3. (4) Adele: '19'
4. (3) Lady GaGa: 'Born This Way'
5. (-) The Horrors: 'Skying'
6. (7) Caro Emerald: 'Deleted Scenes From The Cutting Room Floor'
7. (6) Bruno Mars: 'Doo Wops & Hooligans'
8. (12) Foo Fighters: 'Wasting Light'
9. (5) Take That: 'Progress'
10. (8) Rihanna: 'Loud'
Source: Official Charts Company
> This week's singles chart
Watch a performance of 'Someone Like You' from Adele's number one album 21 below: