Glen Powell Says Relationship With Actress Michelle Randolph is 'Very Serious'

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.

They turned their relationship up a notch when Glen posted PDA-packed pics of the pair partying on the Fourth of July ... the only fireworks many of their fans cared to see.