The British actor beat off several well established heartthrobs, including Brad Pitt and Johnny Depp, to claim the title in a poll conducted by Britain's Glamour magazine.
The 23-year-old year-old star - who shot to fame playing vampire Edward Cullen in teen romantic thriller "Twilight" - isn't fazed by his new sexy symbol status.
He said: "The hottest actor stuff doesn't really mean anything. You have a month maybe with all this heat and hype."
Depp, 46, and 45-year-old Pitt came second and fifth respectively.
Other hunks to make the top ten include Hugh Jackman - who was named People magazine's Sexiest Man Alive last year - soccer superstar David Beckham, Zac Efron and George Clooney.
The Glamour poll asked 2,000 British women to list the man they found most attractive.
Becoming vampire Edward in "Twilight" has led Robert to some interesting run-ins with fans who have crushes on him.
He recently said: "People ambush me and try and find out what hotel I'm staying at, as well as wanting to touch my hair. Everyone just screams and screams. It feels surreal.
"Once there were four girls, in Chicago I think, and they had all scratched their necks until they bled.
"Then when they came up to me they had these bleeding scabs. It was gross."
Glamour magazine's Sexiest Man In The World 2009:
1) Robert Pattinson
2) Johnny Depp
3) Hugh Jackman
4) David Beckham
5) Brad Pitt
6) Zac Efron
7) George Clooney
8) Chace Crawford
9) Justin Timberlake
10) Colin Firth
(China Daily/Agencies August 6, 2009)
