Seth Rogen, Adam Levine & Channing Tatum in Running for Jonah Hilll's Best Man After Engagement

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Jonah Hill just made one of the most important decisions in his life when he popped the question to his girlfriend and asked her to be his wife ... now he's got an even bigger decision to make -- which one of his celebrity friends will be the best man?!

The "Wolf of Wall Street" star is set to tie the knot with girlfriend, Gianna Santos, according to Page Six.

Hill and Santos have been dating since last summer. She's an art director and fashion stylist, who has worked on campaigns for Puma, Converse, Nike and Kith.

There are no details yet on when and where the wedding will take place, as Hill is notoriously private.

However, he will have a big challenge ahead as he chooses a best man ... and as we see it, he's got 4 big celebrities in the running to stand by his side when he says, "I do."

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Seth Rogen has been working with Jonah Hill for years, and the two have developed a strong friendship.

Along with appearing together in many of the Apatow Mafia movies, including "Knocked Up" and "40-Year-Old Virgin," Hill began starring in movies that Rogen had written and produced, like "Superbad."

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Channing Tatum and Jonah Hill have been in a ton of projects together, and have attributed the constant dual projects to their longstanding friendship.

Along with the "21 Jump Street" movies, they also appeared together in "This Is the End" and "Hail, Caesar!"

When Tatum was still married to Jenna Dewan, she once even joked that she felt like a third wheel between his bromance with Hill.

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Adam Levine may be the most obvious choice for Hill to pick as his best man.

The two have been seriously close since childhood, and Hill has regularly spoken on his love for Levine and how he considers him a brother.

Levine and Maroon 5 was formerly managed by Hill's late brother, Jordan Feldstein, and after his death have only grown closer.

If Levine is not chosen as the best man, it's possible he could play another big role, as Hill actually officiated the wedding between the ex "The Voice" judge and his wife, Behati Prinsloo.

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Coming in as the dark horse to get the best man slot -- Leo DiCaprio.

Even though Leo may be Hill's newest close pal, after the two starred in "Wolf of Wall Street," they have developed a strong friendship that has gone past a working relationship.

Hill has even dished on Leo's epic yacht parties, which is a strong quality you want when choosing a best man.

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Brad Pitt would normally be a front-runner in any other competition, but he may be slightly bested by the other stars.

He's included because Pitt and Hill did become close while filming "Moneyball," which has kept them close throughout the years.

However, Pitt has a lot on his mind these days, so he may be hard to lock down.

Choose wisely, Jonah.

Also, congratulations!