Samsung has sold more than 40 million Galaxy S3 Smartphones

"After the incredible success of the Samsung Galaxy S III (S3) Android Smartphone, which sold over 40 million units worldwide, Samsung returns with its new flagship, the Samsung Galaxy S IV (S4)."

Source:  Statement on the launch site for the Galaxy S4, retrieved 5th March 2013

Earlier - 20m sold in 100 days - Sept 2012