One Direction are reaping the rewards of their American success, earning £5m each in the last year, according to the Sunday Times Young Music Rich List.
Band members Harry Styles, Niall Horan and Liam Payne, 19, Zayn Malik, 20, and Louis Tomlinson, 21, rose to fame on The X Factor in 2010.
Their platinum-selling albums Up All Night and Take Me Home both went to number one in the US, catapulting them onto the list for the first time.
But the pop stars still have a way to go before they catch Adele, who tops the list of artists aged 30 or under with a £30m fortune.
The Someone Like You singer made £10m last year, despite taking much of it off to recover from a throat operation and have a baby.
The 24-year-old is worth twice as much as former Girls Aloud singer Cheryl Cole, whose fortune is estimated at £14m, while Leona Lewis and Katie Melua are both worth £12m.
Other new entries to the list of young music millionaires include Emeli Sande and Ed Sheeran, who are both worth £5m.
Sir Paul McCartney is the richest music millionaire overall, sharing a £680m fortune with his wife Nancy Shevell.
The former Beatle has topped the list every year since 1989 and is worth £60m more than Andrew Lloyd Webber, who ranks second.
Irish rockers U2 are third with a £520m fortune, with Sir Elton John fourth (£240m) and David and Victoria Beckham fifth (£200m).