Is Jeff Bridges The Dude? Or is The Dude Jeff Bridges? Either way, ever since playing the iconic role in 1998’s “The Big Lebowski,” Bridges has become a go-to cinematic sage. He’s the guy you cast when your character has wisdom to impart and also the mellowness to not be too in-anyone’s-face about it.

He plays that part in “The Only Living Boy in New York,” a new romantic comedy from director Marc Webb (“The Amazing Spider-Man”). As a hard-drinking and mysterious novelist living in the apartment building of the college-grad main character (Callum Turner), he takes the younger man under his wing and gives him advice on life, writing and love — mostly love, which is unsurprising from the director who broke out in 2009 with the indie rom-com “500 Days of Summer.”

“Jeff’s ethereal rasp just feels like wisdom with a capital W,” Webb tells The Post. “ More importantly, there’s a compassionate dignity and a lack of meanness — what a millennial might call ‘chill’ — that’s very much a part of Jeff the actor. You can’t help but pick up on that in most of his performances, and it just feels good.”

Bridges also serves as the film’s narrator, observing that New York has undergone a radical change in recent years: “It was art against commerce, and commerce won.”

“I’ve noticed it changing,” Bridges, 67, tells The Post, referring to the city. “But that’s inevitable. I’ve seen that happen to my hometown, LA, as well. I still love New York. I’ve been making movies here for a long time — my dad, Lloyd Bridges, used to do plays here.”

With his many roles as a giver of advice, guidance and good vibes (including actually playing The Giver in “The Giver”), we wondered who Bridges himself holds up as a mentor? “I’ve got a buddy who comes to mind,” he says, “Bernie Glassman — he happens to be a Zen master. We met 10 or 15 years ago, and we wrote a book together [“The Dude and the Zen Master”]. He’s a wonderful touchstone.”

Bridges is a longtime meditator, though not as orthodox as Glassman. “My brand is not strictly Zen. There’s some Tibetan, and there’s my own trip as well,” he says, sounding ever more Dude-like. “But I sit. I enjoy that.”

He also cites the Los Angeles artist Rozzell Sykes as a mentor. “He passed away 20 or more years ago, but when I was about Callum Turner’s age [27], my girlfriend was working with him, and he would invite me to play my guitar while he painted. He took me over to his place, called St. Elmo Village, where he’d just transformed his humble living abode into an art piece. Every surface. And he taught me that it’s not about how much stuff do you have, it’s about making the most beautiful art you can with it. He did that with his whole life. That’s very similar to Bernie’s philosophy.”

Bridges, a seven-time Oscar nominee who won in 2010 for “Crazy Heart,” finds his own peace of mind living on a ranch in Montana with his wife of 40 years, Susan Geston, with whom he has three daughters. He’s even gotten involved in helping tourists there learn to be more savvy about wildlife. After making the awards-circuit rounds with the Oscar-nominated Western “Hell or High Water” earlier this year, he appeared in a bear-spray PSA for Yellowstone National Park (“A bear doesn’t care if you’re a movie star,” says the poster with Bridges’ face on it).

“It’s wonderful to be alive with these great animals around, and to just coexist,” he says. “Fortunately, I’ve seen grizzlies around. We’ve even had bears in our yard, sitting up in our apple trees — those weren’t grizzlies of course, they were black bears.”

He also recently spent time in the desert of New Mexico shooting the film “Only the Brave,” out in October, based on the real-life story of firefighters in Arizona, alongside Josh Brolin and Jennifer Connelly. “Josh and I had worked together in a Coen brothers movie [‘True Grit’], so it was great to get together again on this,” Bridges says. “I play the fire chief, the head dog, so I’m not in the action as much as Josh and the other guys.”

He’s also in the secret-agent sequel “Kingsman: The Golden Circle,” out next month, playing a character named Agent Champagne. “I’m the American version of the Kingsmen; our cover is that we make bourbon in Kentucky,” he says. “I don’t [drink] much of that anymore, but I did when we went down there. We went to the Kentucky Derby. We had some mint juleps.”

He also made a casual bet. “It was a name thing,” he says. “I’m curious about sleep; I made this record a few years ago called Sleeping Tapes, which kinda takes on the whole subject of sleep. So I was looking at the menu of horses and saw the name Always Dreaming. I liked that. And I won!”