The South Korean tech giant said the S21, which was released here on January 29, achieved the milestone 57 days after its launch, about one-month faster than its predecessor the S20.
Galaxy S21 sales are estimated to be 40 per cent larger than those of the Galaxy S20, which sold about 1.7 million units last year, according to market tracker Counterpoint Research.
Mega group BTS was featured throughout the online event in demonstrations of the new phones as well as Samsung's new wireless earbuds, Galaxy Buds Pro.
The new flagship series comes with a new design, an epic pro-grade camera for users of any skill level and the most advanced processor ever in a Galaxy device.
Samsung, also the world's largest smartphone vendor, is likely to report an operating income of 9.74 trillion won ($8.95 billion) during the fourth quarter of last year, up 36.8 per cent from a year earlier.
Those who pre-book can get up to $700 of instant trade-in credit toward the purchase of a Galaxy S21 "if you trade an iPhone 12 series phone, or one of Samsung's own Note 20 and S20 phones".