Matt Damon says ‘it was hell’ kissing Scarlett Johansson

He kissed — and told.

“Oppenheimer” star Matt Damon dished about locking lips with erstwhile Marvel co-star Scarlett Johansson, while on the stump for Christopher Nolan‘s smash historic pic.

On an “Agree to Disagree” segment for LADBible with Emily Blunt, who also stars in the thinking man’s blockbuster, Damon was asked whether or not you should tell someone when they have bad breath.

Blunt and Damon didn’t hesitate to insist that you should always tell someone if their breath smells — which Blunt argued is particularly important while filming “intimate scenes” with co-stars.

“There’s an etiquette,” Blunt said. “You’ve got to brush your teeth, use some mouthwash and stick some gum on the roof of your mouth.”

The conversation led Damon to recall the time he wound up kissing ScarJo in a professional capacity, on the set of “We Bought a Zoo.” The former Black Widow played Damon’s love interest in the film.

“I had to kiss Scarlett Johansson,” Damon joked. “Can you imagine how horrible that was for me?”

He continued, “It was hell! What happened was we did a shot before lunch and it was this nice little two-shot that ended in the kiss, and it was really good. We went to lunch. She and I both thought it was over, and she ate, like, an onion sandwich for lunch.”

“She came in and [director] Cameron Crowe had set the camera up, and it was a tight shot of the kiss … She goes ‘Oh, s – – t! I had an onion sandwich!’”

According to Damon, however, Johansson’s breath still smelled “like roses.”