The South Korean's viral hit has become the 129th song to pass the sales milestone in the UK, making him the first Asian artist to do so.
"This is an amazing achievement by Psy," commented Martin Talbot, managing director of the Official Charts Company.
"It is further confirmation of 'Gangnam Style' as a true phenomenon - it is the first UK million-seller by a Korean star, and a sign that K-Pop has truly arrived in the UK!"
'Gangnam Style' only remained at number one for a week in the UK, but went on to spend a further 17 weeks in the Top 10.
The track has topped the charts in 27 countries, including Australia, Germany, France, Mexico, Spain, South Korea and Canada.
The accompanying music video was the first ever clip to pass a billion views on YouTube back on December 21, 2012.
Watch the music video for Psy's 'Gangnam Style' below: