Millie Bobby Brown is ringing in adulthood with a childhood classic.
The pair channeled the cover of a romance novel, with Brown donning a blonde wig and an embroidered corset over a lacy white dress. Bongiovi, 19, wore a brown floral-printed shirt.
"Ur rly pretty," Bongiovi, the son of Jon Bon Jovi, commented on Brown's post.
Her friends, including a few Stranger Things costars, also flooded the comment section with celebratory messages. "Birthday girl," Noah Schnapp wrote. "Say what!?" remarked Matthew Modine. "Loves it," Paris Hilton commented. "Happy birthday lovely!" Emma Bunton added.
Brown and Bongiovi were first romantically linked last June when they were spotted holding hands, after he posted a photo of them captioned "bff <3" earlier that month. They made their relationship Instagram official in November when she posted a photo of him planting a kiss on her cheek while they rode the London Eye ferris wheel.
The couple most recently celebrated Christmas together, with Brown sharing a sweet selfie of the two of them cuddled up in front of the tree. "Happy holidays," she wrote in the caption.
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She's currently gearing up for the premiere of Stranger Things season 4, which Netflix announced is debuting in two parts on May 27 and July 1. The streaming giant also revealed that the show will end after its fifth season.
Brown previously opened up to PEOPLE about growing up in the spotlight. "I think I'm becoming stronger," she said in 2020. "It's difficult because I'm still growing. I haven't evaluated that yet so I'll get back to you."