The company said the 2006 record, which included such hits as "Rehab", "Back to Black" and "Love Is a Losing Game" and netted Winehouse five Grammys, had sold 3.26 million copies, surpassing James Blunt's "Back to Bedlam" (3.25 million).
Winehouse's album shot back to the top of the British charts following her death aged 27 on July 23.
Dido's "No Angel" -- released in the UK in February 2001 -- is the third best-selling album of the century with sales of 3.07 million in the UK.