Like a fine wine, Louis Garrel‘s “A Faithful Man” needs to be opened to the elements, to “breathe.”

Because if there’s ever been a more airless, so-dry-one-hesitates-to-label-it “romantic comedy,” I’ve yet to set parched eyes upon it.

It is very French, with a ménage á trois, naturellement. It has a few laughs, or at least chuckles. But the deadpan has only 75 minutes to pay off. Letting in a little air would not have unraveled the script’s peculiar, cultural difference qualities. But it might have made it funnier and let it go down easier.

Garrel, an actor (“The Dreamers”) turned actor-director (“Two Friends”) plays Abel, and we meet him as he narrates his oddly emotionless college breakup with Marianne (Laetitia Casta, who is married to Garrel).

They were together three years, and “Things were fine, until one day” she tells him (in French, with English subtitles), “I’m pregnant.”

It’s not his. It is to be the baby of his best friend, Paul. Oh, and Paul wants you to come to the wedding.

Perhaps Garrel just isn’t a funny enough actor to make Abel’s under-reaction to all that score.

“When is it?”

She adds, “I’m glad you’re taking this well.” And “Can he call you today?”

“Maybe not today.”

I mean, we know the French are supposed to be oh-so-sophisticated about things like this, even in their 20s, but come on.

Abel saves his heartbreak for his icy, nosebleeding,  “What a loser” exit.

The one person who sees that is Paul’s little sister. Years pass, Paul dies, leaving Marianne with a son (Joseph Engel) Abel meets at the funeral.

Because, naturellement, he shows up. He narrates his continuing love for Marianne and wonders how he can wangle his way back into her life.

But there’s Paul’s baby sister Eve (Lily-Rose Depp).

“I knew her as a child, she had become a woman.”

So even though he’s all-in on Marianne, our story shifts narrators (all three principals eventually narrate), and Eve tells us of her childhood crush on “the most attractive man alive.”

Beware co-writer/directors who script such a description of themselves to be delivered by the beautiful daughter of Vanessa Paradis and Johnny You-Know-Who. It might be ironically intended, but it doesn’t play that way.

And that doesn’t lessen the picture’s inherently iffy — from an American #MeToo point of view — crush to have Eve tell us, “I did only one thing well…I grew up.”

The leading ladies outshine the leading man in “A Faithful Man,” with young Ms Depp showing promise if not a lot of spark, here.

Voice-over narration, the cinema’s laziest storytelling device, is meant to move this along by EXPLAINING all that is happening — “We chatted during lunch. About Paul, of course.” — when the actors as characters could be SHOWING us with their performances, the situations and witty dialogue.

There’s a little of that here. The funniest thing in “A Faithful Man” is all the scenes that paint Abel as a gullible, passive drone, borderline “on the spectrum.”

Girlfriend of three years is preggers with your best friend’s baby? And she’s marrying him?

The kid is plainly playing Abel when the first time Marianne leaves the two of them alone, he whispers, “Mom poisoned dad” and the reason nobody found out is “she was sleeping with the doctor” who signed off on his father’s death.

Garrel could be playing around with the cliches of French romances — ducking into the cinema to watch classic Hollywood film noirs (“The Strange Love of Martha Ivers”) — or maybe not.

I couldn’t decide if he was having us on, even if he gives us a hint he might be, here and there.

I couldn’t decide because his movie’s too brief to flesh out the stories, find funnier lines or beef up the comedy. And never once, in all the characters’ incessant narration, does anybody say, “Drôle, non?”

MPAA Rating: unrated

Cast: Louis Garrel, Lily-Rose Depp, Laetitia Casta

Credits: Directed by Louis Garrel, script by Jean-Claude Carrière, Louis Garrel. A Kino-Lorber release.

Running time: 1:15