Sebastian Stan Says He Shaved Head for Role, Not Midlife Crisis

Sebastian Stan fans can rest easy ... the star isn't having a Britney Spears-level meltdown -- 'cause he only shaved his head for a role.

We caught up with the actor in West Los Angeles Wednesday ... and, we had to ask him about his new bald head since ladies loved his luscious locks.

Stan tells us he shaved it all off for a new role, though he didn't go into detail on what that role might be. However, he's clear -- this isn't a midlife crisis ... at least, not yet, he jokes.

We also asked him what happened to his hair ... and, he says he doesn't know -- so, keep an eye on eBay in case an opportunist nabbed a lock to flip it for a profit.

Like we said, unclear what the role is that prompted Sebastian to shave his head ... but, we do know "Avengers: Doomsday" started filming recently -- so, maybe Bucky Barnes is tired of hair getting in his eyes when he's fighting a big bad. Of course, "Thunderbolts*" comes out tonight, and it looks like he's still got all of his hair for that Marvel entry.

He's also starring in the upcoming psychological horror movie "Let the Evil Go West" ... and, many fans might feel the biggest evil is being deprived of seeing Sebastian's flow.