There’s a new man in town in “Stranger Things” and — inconceivable! — it’s the Dread Pirate Roberts.

Cary Elwes, who rose to fame playing Westley, the farm boy turned pirate in the endlessly quotable 1987 classic “The Princess Bride,” has joined the Netflix hit series, which begins Season 3 on July 4.

“My wife and I had binge-watched it,” says Elwes, 56, who lives in California with his wife, photographer Lisa Marie Kurbikoff, and their daughter. “We totally got into it. That was the first time we watched a show where we absolutely canceled everything.

“Who wouldn’t want to join this show?”

The new season of “Stranger Things” sees the small town of Hawkins, Ind., equipped with a new mall, new supernatural threats and a new character, Elwes’ Mayor Larry Kline.

But don’t expect to hear Kline say “as you wish,” Elwes’ wistful “Princess Bride” catchphrase. This mayor is a corrupt, cocaine-sniffing, ’80s politician who lives in a large house with garish, animal-print decor, and who loves frustrating the show’s kindhearted grump, Police Chief Hopper (David Harbour).

“David is wonderful,” says Elwes, who’s also known for “Robin Hood: Men in Tights” and “Saw,” and who will figure in the third season of “The Marvelous Mrs. Maisel.” “I admired him from before we started working together.”

Elwes says the main reason he signed on to “Stranger Things” was his affection for the people in the story. “You’re so invested in these characters,” he says. “If you weren’t, it would just be some run-of-the-mill horror thing. But because we’ve watched these kids grow up, they feel like family. Kline is a wonderful foil for Hopper. The chief is somebody who does care deeply about the community. It’s a nice contrast to have a mayor who doesn’t.”

Although he stops short of naming names, Elwes says he drew from real-life politicians to craft Mayor Kline. “I watch a lot of CNN,” he says. “You can go to any part of the world and there are politicians who are — let’s put it this way — more interested in themselves than their community.”

He’s also the perfect actor for a show steeped in ’80s nostalgia, thanks to “The Princess Bride,” whose fans love to quote his character’s lines to him. Then again, Elwes tells The Post, he’s luckier than his “Princess Bride” co-star, Wallace Shawn, who has people yelling “inconceivable” to him all the time.

“I have three words that mean ‘I love you,’ ” he says of his catch phrase. “And that’s pretty nice.

“It’s funny,” he adds. “As I get older, I get it more and more . . . It used to be sort of weekly, and now it’s once every few days. It’s wonderful — I call it the gift that keeps on giving. I think you’re lucky as an actor to have any of your work resonate with anyone. And the fact that this is over 30 years ago is really phenomenal.”

Filming the ’80’s-era Netflix show also brought back memories of his own time during that decade, which the London-born actor spent in New York City, studying at Sarah Lawrence College and the Lee Strasberg Theatre & Film Institute.

“I spent most of the ’80s, believe it or not, in Manhattan. Reading your paper [The Post] and exploring a new life in America. I was in Tribeca before it got gentrified. My rent was so low, you couldn’t get a closet for what I was paying today. It was fun. I was studying. I was exploring the city and all the wonderful things Manhattan has to offer in terms of culture. It was a great time for me.”

The only thing he doesn’t miss, he says, are some of his hairstyles and jackets with shoulder pads.

“All those photographs have been destroyed,” he says.