The 17-year-old singer, real name Ella Yelich-O'Connor, topped the American list which Billboard says is an "annual ranking of music's most powerful minors", reported Billboard magazine.
Last year, the 'Royals' hitmaker came in at number six.
She has beaten the likes of boyband Seconds of Summer to land the title, which ranks the hottest young stars of the year.
Justin Bieber places third on the countdown, with Dutch electronic DJ/producer Martin Garrix and girl group Fifth Harmony rounding out the top five.
"Lorde has used her debut single as a springboard to unequivocal superstardom," Billboard said.