It’s not easy playing the father of all barbarians.

When Jason Momoa signed on to star in “Conan the Barbarian,” a character he has loved since childhood, the Hawaii-born actor joined a franchise made famous by eight decades of paperbacks, comic books, paintings, graphic novels and two movies starring Arnold Schwarzenegger.

There are legions of fans who will compare him to every Conan there ever was, but Momoa hopes they’ll end up comparing him to every Conan there ever will be. That was Momoa’s goal when he auditioned for the movie, which was adapted from works initially published in 1932 by Texas author Robert E. Howard.

The film from Lionsgate and Millennium Films opens nationwide today. It’s Momoa’s first time on the big screen.

“I don’t think anyone can play Conan better than me and that’s what I wanted to do,” Momoa said in a phone call from Los Angeles. “I know there are a lot of people who are big fans of Conan and I think people will love it.”

But securing the part was far from easy.

Although the 32-year-old Momoa had already been cast as Khal Drogo, a fierce, hulking warlord in HBO’s “Game of Thrones,” studio executives at Lionsgate felt he was too unknown. The actor’s critics couldn’t forget his previous roles. A former model, Momoa got his start in 1999 as a lifeguard on “Baywatch Hawaii” and was featured for two years as a dreadlock-sporting alien in “Stargate: Atlantis.”

The doubt subsided slightly when “Game of Thrones” became a huge hit.

“I’ve been the underdog since day one,” he said. “When I got signed on for Conan it was like, ‘What? He is from ‘Baywatch’ and ‘Stargate,’ he can’t play Conan. And he can’t play Drogo.’ It’s just people with narrow minds. They don’t know anything about me.”

Momoa’s only support came from the film’s director, Marcus Nispel, whose horror films — recent remakes of “The Texas Chainsaw Massacre” and “Friday the 13th” — were box-office hits.

Nispel had looked at hundreds of actors around the world — as far away as Russia, Europe, even Iraq — by the time he found Momoa in Topanga, Calif., five miles from his own home.

“I set up the screen test, which I paid for myself because no one wanted him at the time,” Nispel said. “He was on nobody’s radar.”

Momoa arrived at the screen test with his own sword.

“We shot it at Frank Sinatra’s mansion where I did a Loreal commercial and he took an entire hedge and a tree apart,” Nispel said. “And at the end he did a haka and it scared the crap out of me.”

AND STILL, the critics formed a chorus. They said Momoa looked like a pirate, Nispel said.

“I said, ‘You just have to meet him in person,’” the director said. “When he came to Lionsgate and walked past all these cubicles, every girl, every secretary went nuts.”

In Momoa, the director found the feral confidence he saw in Conan. And one more thing.

“It’s chutzpah,” Nispel said. “If you don’t have that, you can have the best bodybuilder in the world, you can have the best actor in the world but you will not be able to tell this movie because this movie is written for a politically incorrect kind of guy. Like early James Bond.”

Momoa, who is 6-foot-4, brought more than swagger to Conan. In the six weeks he had to prepare before filming began in Bulgaria, he trained six hours a day. He lifted weights, did cardio and perfected martial arts fighting stances that included swordplay.

“I would never voluntarily try to be in that kind of shape,” he said. “It’s too time consuming. I just don’t have the drive to do that. But as an actor, it’s fun to go there.”

He wound up a lean 235 pounds but he wasn’t preparing for a bodybuilding contest. Instead, Momoa was thinking more like a samurai with the predatory qualities of large cats. He watched old samurai movies and would take his daughters to the zoo, where they would watch the lions.

“I really wanted to be nimble and quick,” Momoa said. “Not too big. Just muscular enough to be a product of his environment.”

Rose McGowan, who stars as Conan’s lethal opponent, the half-witch Marique, called Momoa the perfect choice.

“I think Robert E. Howard would have been beyond pleased with the choice of Jason Momoa,” she said.

“I think he just fits. He is a massive man. All muscle.A natural kind of amazing.”

Momoa did most of the stunts himself but there was one part of the action he wasn’t thrilled about: his horse.

The actor hates horses. Hates riding them. He says horses have tried to kill him four times.

“I just don’t trust some other animal holding my life in its hand,” he said.

But Momoa isn’t easily frightened. It’s the horse he used in the film that should be worried, especially if this modern version of the iconic character does well enough to spawn a sequel.

“The first thing that happened when I got on my horse is he reared up and bucked me off and I broke a rib,” Momoa said. “I hate that horse. In fact, in ‘Conan 2,’ I am going to start by eating that horse. I’m going to be eating horse poke.”