The hit, taken from her debut album ‘When We All Fall Asleep, Where Do We Go?‘, was also Spotify’s second-most streamed song worldwide for 2019.
In a statement, the International Federation of the Phonographic Industry (IFPI) hailed Eilish for taking “the world by storm with her incredibly voice and genre-defying sound”.
IFPI chief executive Frances Moore said: “She is also an artist who addresses important issues like mental health in her lyrics that clearly resonate with her fans all over the world.
“We wish her success for what will no doubt be another standout year.”
Second place in IFPI’s ranking was secured by Lil Nas X, whose hit ‘Old Town Road’ racked up some 18.4 million sales last year.
Meanwhile, Eilish recently premiered a powerful video message speaking out against body-shaming during the opening show of her world tour in Miami.
The singer kicked off her ‘Where Do We Go?’ world tour at the American Airlines Arena in the Florida city on Monday night.
The ‘Where Do We Go?’ tour will visit Manchester, Birmingham and London in July for a series of dates.