Glen Powell is known mostly for his funny leading-man roles … but it sounds like his love life is anything but a laughing matter — because he and his new flame are super “serious.”

We caught up with the actor in New York City on Thursday … and we had to ask about his romance with “Landman” star Michelle Randolph — with whom he went Instagram official back in July.

Our cameraperson asked Glen if it was scary to hard launch on Insta — with the whole world waiting with bated breath for the announcement … but he says it’s not. Not if you really believe in it.

It sounds like more than your average summer fling … a fact Glen confirmed when he said point-blank, “I’d say it’s very serious.” Worth noting, we also asked Glen if an engagement might be on the horizon — but he’s keeping that info to himself.

As we reported … Glen and Michelle started fueling dating rumors last year — and they haven’t been afraid to flaunt their new love.

The two stars have been locking lips all over the country … from Austin, Texas, to Miami, Florida, to the Big Apple itself.