The singers have shot to the summit of Heat magazine's Rich List for under-30s with combined earnings estimated at £59.33 million.
Harry Potter star Radcliffe has topped the list since it was established in 2010, but is this year in second place with £56.19 million.
One Direction - soon to release their third album Midnight Memories - were included as a single entry for their total earnings, rather than individually, because the money has been generated by the group rather than for any solo work.
The highest new entry is DJ and music producer Calvin Harris who was number 8 in the list with £22.2 million.
Lucie Cave, editor-in-chief of Heat, said: "One Direction are young, talented, staggeringly good looking and adored by millions. To that we can now add 'rolling in cash'. No one said life was fair."
The stars' financial dealings, including TV shows, movies, record sales and product endorsements, were examined by a panel of industry experts.
The full list is published in Heat tomorrow.
Top 10 Richest British Celebrities under 30, with last year's position in brackets:
1 (5) One Direction, £59.33 million
2 (1) Daniel Radcliffe, £56.19 million
3 (2) Robert Pattinson, £44.16 million
4 (3) Keira Knightley, £37.28 million
5 (4) Emma Watson, £27.93 million
6 (6) Adele, £27.54 million
7 (7) Rupert Grint, £24.09 million
8 (-) Calvin Harris, £22.21 million
9 (9) Cheryl Cole, £15.50 million
10 (8) Leona Lewis, £14.45 million