Each year, the publication compiles a list of the 30 "brightest" young talents across 15 categories including Music, Education, Law & Policy and Social Entrepreneurs.
Claflin, who will play Finnick Odair in the upcoming Hunger Games sequel Catching Fire, made the list alongside Girls co-creator Dunham and X-Men: First Class star Hoult.
Other notable names included Logan Lerman (The Perks of Being a Wallflower), Rebel Wilson (Pitch Perfect), Chloe Moretz (Hugo), Nev Schulman (Catfish) and Glee actor Chris Colfer, who penned and starred in recent comedy Struck by Lightning.
Forbes's 30 Under 30 Hollywood list is as follows:
Ian Hecox, Anthony Padilla
> 'Hunger Games: Catching Fire' casts Sam Claflin as Finnick Odair
> Lena Dunham threatens Gawker with lawsuit over leaked book proposal
Watch a trailer for Snow White and the Huntsman, featuring Claflin, below: