21 added another 130,000 copies to its tally over the last seven days, making Adele the first UK female artist to have an album at number one for more than two weeks since Susan Boyle and her 2009 debut I Dreamed A Dream.
New entries on the chart this week include Computers And Blues, the final album from The Streets at eight, while James Blake - who finished runner-up to singles chart champion Jessie J in the BBC Sound Of 2011 contest - lands at nine with his self-titled debut record.
Just behind them is the phenomenally successful Progress by Take That, which climbs up three spaces to return to the top ten in its 13th week of release.
Elsewhere, the run-up to Valentine's Day sees Roberta Flack and Michael Bublé experience significant boosts in sales, as the former's Love Songs jumps nine places to 11, while Bublé's Crazy Love is at 20 from last week's 25, 69 weeks after its release.
Sandwiched between them is another romantic record, UB40's 2009 compilation Love Songs, which makes a triumphant return to the top 40 at 16.
However, Ellie Goulding and Cee Lo Green both take mighty tumbles down the chart, as Lights and The Lady Killer fall seven and eight places respectively to 14 and 18.
The top ten in full:
1. (1) Adele: '21'
2. (3) Bruno Mars: 'Doo Wops & Holligans'
3. (5) Rihanna: 'Loud'
4. (6) Eva Cassidy: 'Simply Eva'
5. (2) Chase & Status: 'No More Idols'
6. (4) Adele: '19'
7. (9) Rumer: 'Seasons Of My Soul'
8. (-) The Streets: 'Computers And Blues'
9. (-) James Blake: 'James Blake'
10. (13) Take That: 'Progress'
Source: Official Charts Company
> Click here for this week's singles chart