The 30 smartest celebrities in Hollywood

Natalie Portman had already started her Hollywood career when she graduated from Harvard with a psychology degree.

And before John Legend was a Grammy Award-winning artist, he worked for a consulting firm. 

We rounded up 30 of the smartest celebrities in Hollywood who are high-school valedictorians, Ivy Leaguers, MENSA members, and certified geniuses in their own rights.

Here they are:

(Melissa Stanger originally contributed to an earlier version of this slideshow.)

Emma Watson did Hermione proud during her studies at Brown.

In May 2014, the "Harry Potter" actress walked across the commencement stage at Brown University, where she earned a bachelor's in English literature. She also pursued studies at Oxford University during her Ivy years, and took a year off in 2011 to film.

Later that year, Watson was appointed UN Women Goodwill Ambassador, and gave an impassioned speech about women's rights. As part of her new role, she helped launch the HeForShe campaign.

Conan O'Brien graduated magna cum laude from Harvard.

Legendary late-night host Conan O'Brien, who was his high school's valedictorian, attended Harvard as a history and literature major. The school newspaper dubbed him the "pre-eminent jokester" of the class of 1985, which makes sense, as he was also the president of the Harvard Lampoon, a semi-secret social organization that published a humor magazine.

His 72-page senior thesis, "The 'Old Child' in Faulkner and O'Connor," argued that "the New South's emerging identity is manifested in the literature of William Faulkner and Flannery O'Connor via the motif of children that age too quickly."

Allison Williams is more than the smart one on "Girls."

Growing up, the "Girls" actress wasn't allowed to act professionally until she graduated from college. She studied English and archaeology at Yale — taking the kind of classes that make you feel like "lying on the ground thinking about things,"she said.

When she didn't get a part in Yale's big musical as a freshman, she joined the improv group instead and found she had a knack for comedy.