The 23-year-old is said to have earned around 25 million pounds just for his role in the two "Deathly Hallows" films.
Radcliffe is followed by "Twilight" star Robert Pattinson, 26, in second and actress Keira Knightley, 27, in third in the Heat magazine's list of 30 richest British stars under the age of 30.
Emma Watson, 22, retains fourth place with a fortune of 26.5 million pounds.
Boy band group One Direction are the highest new entry, placed at number five by amassing a fortune of 26.3 million pounds in the last year.
The Heat rich list is compiled by a panel of industry experts who have analysed the stars' financial affairs.
Adele, 24, who gave birth to her first child last week, is at sixth place on the list. Her estimated earnings stand at 26 million pounds, an increase of 18.4 million pounds on last year.
