“The bottom line is that it’s just fucking great writing,” Jake Gyllenhaal says of his American stage debut, Off-Broadway play “If There Is I Haven’t Found It Yet.”

Gyllenhaal stars as the couch-crashing Uncle Terry in Nick Payne’s British drama, opposite Brían F. O’Byrne, Michelle Gomez, and Annie Funke. “It’s about family,” Gyllenhaal says. “I think family is the most important thing in the world. I think your own family is the most complicated thing in the world, and I think it’s the most beautiful thing in the world. I think it’s what I love the most.

“Somebody was trying to get an angle on why I moved to New York, and I was like, ‘Because my family is here and I love them. And I want to be with them and they mean everything to me.’

This is the best possible place for me to be, to be near my family, doing a show about the mess of a family, and then maybe having my family come watch it.”

As for his newly acquired stage relatives, Gyllenhaal can’t rave enough. “These actors are fucking amazing. Wonderful! And I’m a harsh critic, you know? I am. And they’re probably just as harsh as I am. But so far it’s been wonderful.”

The four-person dramedy, set in England and directed by Michael Longhurst, has what Gyllenhaal calls an ambitious physical production. “It takes what you sort of assume the play is going to be and it makes it so much bigger and grander. As much as I am one for real human interaction, I also want to make a show that’s entertaining and that people want to see,” Gyllenhaal says. “And I don’t think anyone here has any desire to make some quirky family drama. That’s not what it’s about. And Michael has done it. It’s ambitious. It’s daunting for us because I think we have to pull a lot of stuff off.” He laughs, adding, “But it’s not like ‘De La Guarda’ or anything.”