“You can make a killing in the theater, but you can’t make a living.” — Robert Anderson

He was here for this year’s annual International Film Festival. There’s hardly a spot in television where he isn’t lurking somewhere in the hall. He’s Irish-born (Dublin), and one of our great international film stars.

He’s been a priest, spy, doctor, lawyer, killer and psychiatrist, and we remember him most for the centerpiece of 1995’s “The Usual Suspects.”

He’s Gabriel Byrne, and he’s back in town in his greatest, most human part yet, that of a down-at-the-heels, end-of-his-rope, New York actor, in director Lee Wilkof’s and writer Ethan Sandler’s very good comedy-drama “No Pay, Nudity.”

Here, Gabriel plays Lester Rosenthal, one of the millions of faceless souls that roam the sidewalks of the coldest place in America: Manhattan.

Full disclosure: This writer was one of this gang for 10 years in Manhattan’s indifferent world of theater, where you are alive when you’re working and dead and faceless when your show closes.

Each year, the hordes of Lester Rosenthal types prowl the sidewalks looking for a job, any job. No Pay? Nudity? We’ll take it. How many weeks, hours? How many lines? Two? We’ll take it. No pay? Who cares?

If it runs long enough, someone may come and see you, an agent, a producer, maybe just your mother.

But some are lucky if you call it that. They have been there so long, so many luckless years, that they’ve managed to hold on to pre-war rent-controlled walk ups. Leonard is one of those.

Leonard is divorced. Of course, he is. She left him long ago. Leonard has a daughter (Zoe Perry) who occasionally drops by to fill his fridge with real food instead of his frozen dinners. She offers a job as a waiter in the restaurant where she works. He won’t go back to that.

Leonard’s wardrobe has grown outdated and his cuffs, both on his sleeves and pants, are beginning to thin.

So each day, Leonard, who previously had a soap opera run as a doctor, spends the hot hours of the day hanging out with others of his kind, in the Actors’ Equity Lounge on the 16th floor on West 46th Street, with a nice view of the theater district.

There are lounge facilities here where Leonard sits with his friends; some are new, some have been sitting here so long they have their own spots that nobody dares take away.

One of these belongs to an overweight, long-out-of-work player from the ’50s, who is simply known as Herschel (a wonderful, joyful, delicious Nathan Lane).

There is Andrea (Frances Conroy, a Tony Award-winning Broadway actor you probably remember as the mother in “How I Met Your Mother,” Mom in “Six Feet Under,” and Virginia in “Desperate Housewives”) who comes each day with her puppy and mothers the lost souls who drift in and out.

Broadway star Donna Murphy is there as a singer/dancer/actress being coached by Leonard, who has taken over a friend’s acting class for a week. We hope for a romance. Really? Don’t count on it. He’s grown too old to be a prime date magnet.

A ray of sunshine breaks through the clouds when he auditions for the lead in Shakespeare’s “King Lear.” He is hired, but only to play the lesser part of the Fool, in a local theater in his hometown back in Ohio, every actor’s nightmare.

He takes it, and hometown players from his past open another chapter.

All the players in the film are perfectly cast, as real as the rain — especially Lane. But it’s Byrne who stuns all of us in his portrayal of Leonard Rosenthal, a poignant, heart-tugging rendition of an aging man with a bad haircut, caught up in a world of unrequited love.

It’s clear that if Gabriel Byrne hangs on, he will continue to stun us long into his final hours.

J.P. Devine is a former stage and screen actor and author of “Will Write for Food.”