The British-Irish group, which found fame on The X Factor in the U.K., reached the milestone after selling eight million singles, three million copies of its debut album Up All Night and one million DVDs.
To mark their huge success, the boys were presented with special plaques by bosses at Syco and Sony Music on Wednesday.
Singer Liam Payne says, "We are obviously ecstatic and incredibly humbled by our award. We have an incredible team of people around us who have helped us achieve this, and above all we would like to thank our fans. We owe all our success to them."
The young stars were seen toasting their achievement by partying at London nightclub Chinawhite on Wednesday.
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