She was awarded with a diamond plaque in New York after performing the last of six sell-out shows in Madison Square Garden.
Her 2011 album, 21, also reached diamond status - and according to the Recording Industry Association of America, more than 14 million copies of that record have been sold to date.
No other artist has managed to go diamond platinum once, let alone twice, in 12 years.
Before Adele, the last person to sell 10 million copies of one album was Usher in 2004 - with Eminem and Norah Jones also securing diamond status with their 2002 records.
The soaring popularity of digital music, and streaming services such as Spotify and Apple Music, has made the threshold more difficult to reach.
However, Adele`s decision to keep `25` off streaming services for seven months after its release may have given her sales a boost.
The success of her third studio album, which features singles including Hello and Send My Love (To Your New Lover), has helped cement her status as the century`s top-selling artist.
On Tuesday, it was announced that Adele was nominated in four categories at MTV`s Europe Music Awards - including best song for Hello, and best female act.
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