Will Smith and Forest Whitaker did it on the red carpet at the SAG Awards last month. The men of TV’s “Entourage” embrace it. The Soprano boys take it in stride.

We’re talking about the Man Hug. Dudes hugging dudes. In public and with enthusiasm.

It’s happening more and more, and not only among celebrity guys.

“As American men, we used to have one option for greeting one another: the handshake,” says psychotherapist and pop culture commentator Joshua Estrin. “Not anymore.

“I travel a lot, and I’m seeing it all over the country. You can walk into a Cheesecake Factory in the Midwest and see guys with their girlfriends greeting other guys with hugs. It’s interesting and rather uplifting, I think.”

Hip-hop artists are widely credited with introducing the popular “pound hug” or “pound shake” as a greeting between men. It consists of a combination of a handshake and a stiff one-armed hug, and includes two slaps on the back.

“Depending on the circumstances, it can also include a loud exclamation, a general grunting noise to assert your masculinity,” says Patrick Carone, entertainment director for Stuff magazine, whose readers are largely males in their 20s.

That’s just one of the ways that American Man Hugs are different from hugs between men and women, and even embraces among females, he notes. The accepted protocol? Man Hugs are brief, involve minimal body contact and may include a back slap, a guttural noise, or both.

“We’re still men, after all,” jokes Carone. “It’s OK to show that we like each other, but we still have to act tough.”

Nancy O’Reilly, a clinical psychologist who practices in Missouri, believes in hugs. Hugs, she says, can be magical and healing.

“Studies tell us that hugging and physical intimacy can be extremely powerful” to the psyche, says O’Reilly. “Of course, it can also be scary.”

Especially if you happen to be a guy living in a macho culture.

Affectionate behavior “simply isn’t a part of the masculine gender role,” says Kory Floyd, an associate professor of communication at Arizona State University who has studied the Man Hug phenomenon. “We socialize men to compete,” he says, “not to be affectionate.”

Floyd has documented the types and lengths of hugs between men and found that they rarely involve full body contact or last more than a second.

“They often begin with a handshake that continues through the hug, so they have their hands as a barrier between them,” Floyd notes. Men watching other men hug each other tend to become uncomfortable when the embraces last more than a couple of seconds, he says.

“Research shows that when people see two women hugging in public, they don’t think twice about it,” he says. Seeing two men hugging “is more unexpected, so it causes people to question” why they’re embracing. Specifically, whether the male huggers are more than just friends.

“It all comes down to fear, unfortunately,” says O’Reilly. “Many heterosexual men are fearful of men who are gay, and they’re afraid of being perceived as gay themselves. They’re thinking, “If I really like this guy and want to hug him, is it possible I’m gay?”‘

Those thoughts go out the window when men celebrate sports accomplishments, say O’Reilly and others. What’s more manly, after all, than belting a grand slam or sacking the quarterback? Or acknowledging such feats with a Man Hug?

Vlade Divac, the beloved former Sacramento King, had no qualms about embracing his teammates after a stellar pass or slam dunk. Baseball sluggers Mark McGwire and Sammy Sosa engaged in a famous hug during their home run race.

The American football huddle is a form of group hug, notes Emerson Smith, a sociologist and associate professor of medicine at the University of South Carolina.

“It’s a fraternal hug that protects words from being heard and gestures being seen by the opposing team,” says Smith.

Football games offer good opportunities for men to show unabashed affection toward one another, says “guy’s guy” Cecil Taylor of Sacramento, who hunts and fishes and makes his living installing sprinklers.

“I think it’s OK to hug your buddies for a celebration, like when we’re watching a game and our team wins,” he says.

“It depends on the mood,” Taylor says of the general suitability of Man Hugs. “But the hugs normally are with one arm, and quick. All in all, the meaning is the same. It’s always good to see your friends.”

Today, American men are taking hugs beyond the playing field, thanks to hip-hop, global communication and guys such as Tony Soprano and Ari Gold of “Entourage.” Elaborate handshakes have morphed into half-hugs and full embraces.

The men of “The Sopranos” perform full-on hugs on members of “the family,” in keeping with their Italian heritage. But they’re professional killers. Can regular guys get away with it?

Fuhgeddaboutit.

“Full-on hugs for most guys are pretty tricky,” says Carone. “Unless you just pitched a no-hitter or something like that, you don’t get one, except maybe at a wedding or a funeral, and only among family.”

Airport meetings present interesting scenarios for Man Hugs, he says.

“The length of time that has passed since you last saw the person is the determining factor for if a hug is warranted,” instructs Carone. “If you haven’t seen the person in a long, long time, dropping the bags and giving a Man Hug is OK. But you don’t want to linger. Just a couple of beats. One, two. That’s it.”

Ari Gold and the guys of HBO’s “Entourage” regularly “hug it out” as a gesture of friendship and forgiveness, and their behavior has caught on, says Carone.

“These are the cool guys who rule Hollywood,” he says. “They have the coolest clothes, the fastest cars, the beautiful women. They’re comfortable doing it, so it makes regular guys more apt to think it’s OK.”

The Internet and the global economy have given American men a better window on cultural practices in places where platonic hugs and kisses between males are no big deal, Estrin notes.

The terrorist attacks of 2001 gave men permission to express emotion, he says, and war and general chaos around the world have made everyone feel more vulnerable.

For all of these reasons, “men are much more willing now to connect with one another in a physical way,” he says.

“We’re living in such a difficult time, and it strikes me that we’re all rethinking and redefining what it means to be alive,” says Estrin.

“So if I want to congratulate a friend, I’m not going to ask myself whether I should give him a great big Man Hug. I’m just gonna do it.”