Long a popular actress, Portman got a boost in the standings by her turn in Oscar-winner Black Swan, an indie film made for $13 million US which grossed $329 million at the box office.
Forbes bases its most-bankable ranking on the last three films starring each actor, comparing the cost of the film and the salary paid to the star with its box office results.
Portman’s success is unusual because her other films include Your Highness, which flopped, and No Strings Attached, a rom-com that did surprisingly well.
Most of the top 10 actors on the list had roles in blockbuster franchises.
Second-place actor Kristen Stewart is star of the Twilight franchise and Snow White and the Huntsman and returned an average of $40.60 for every dollar she earned.
She ran a close second to Portman, with the last two Twilight films among her last three films. Snow White also drew a big audience, in part because of interest over her scandalous affair with director Rupert Sanders.
Fellow Twilight star Robert Pattinson is also on the list, along with another Twilight face, Taylor Lautner. Pattinson’s turn in Like Water for Elephants brings him onto the list lower than Stewart, and Lautner had a bit of a failure with Abduction.
Other high-ranking stars include Harry Potter actor Daniel Radcliffe, and Shia LeBeouf, who says he is now finished with the Transformers movies, but counts Dark of the Moon among his last three films.
This list is a counterpoint to Forbes's Most Overpaid Actors list for 2012, which was released earlier this month with Eddie Murphy topping the list.