The lovebirds were spotted out and about in the French capital over the weekend, showing a little PDA as they strolled the streets hand in hand.
Culkin, clad in a black-and-white patterned top and black pants, was all smiles while shopping with Song, who kept it casual in a graphic T-shirt and skinny jeans. The pair couldn't have looked any more adorable, holding hands and rocking matching Converse kicks.
Culkin, 37, and Song, 30, are currently in France for a vacation with a few of their close pals.
The sighting comes less than a week after Culkin revealed that he would love to have kids with the former Disney star someday.
"I'm gonna make some babies," Culkin said during his guest appearance on The Joe Rogan Experience podcast, when asked if he wants children. "This one's a good one, so I'm probably going to put some babies in her in a little bit. I mean, we've definitely been practicing."
He also joked about having mixed-race children, referencing Sean Lennon, the son of the late John Lennon and Yoko Ono.
"This one, I'm going to have some pretty babies," he shared. "She's Asian, so I'm gonna have tiny, little Asian babies. It's going to be adorable -- a bunch of Sean Lennons running around the house, that's what I'm looking for."
Hear more on their relationship in the video below!