The Riverdaleactor took to Instagram on Thursday to share a stunning topless photo of his girlfriend, as well as a sweet message to wish her a happy 22nd birthday. In the artistic snap, a fresh-faced Reinhart looks in the mirror as she covers her upper body with her arms.
"Both the birthday and the gift. My little muse, happy birthday my love," the 26-year-old actor wrote alongside the gorgeous photo, which naturally had Bughead fans going crazy. Reinhart, on her end, replied to the post with a simple, red heart emoji.
Earlier in the day, Sprouse had also posted another captionless snap of the blonde beauty.
The twosome has maintained a relatively private relationship, and has avoided discussing their personal lives during interviews. Their onscreen parents, Skeet Ulrich and Mädchen Amick, who play FP Jones and Alice Cooper, even admitted to ET last month that the actors rarely talked about their romance until recently.
"It's nice that they're able to now, like, be public with it, so it's not so under wraps," Amick said. "But at the same time, they're in complete control of what they want to share and how they want to share it. Behind the scenes, they're so sweet with each other and they're both just exceptional people."