Chris Pratt and Katherine Schwarzenegger Are Instagram Official -- See His Sweet Birthday Post

Chris Pratt and Katherine Schwarzenegger
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The couple was first photographed together in June.

Chris Pratt just made his and Katherine Schwarzenegger's love public!

The Guardians of the Galaxy star took to Instagram on Thursday to wish his girlfriend a happy 29th birthday. Sharing a collage of intimate photos of the two, which include Schwarzenegger giving Pratt a pedicure and both wearing face masks, the 39-year-old actor couldn't help but swoon about how she "lights up the room."

"Happy Birthday Chief! Your smile lights up the room. I’ve cherished our time together," Pratt wrote alongside the collage, which marked the first time he's shared a photo of the two together. "Thrilled God put you in my life. Thankful for the laughs, kisses, talks, hikes, love and care.♥️???."

On Wednesday, a source told ET that the two -- who were first spotted together in June -- are in a "serious relationship and everything is going well," yet Pratt isn't rushing to get engaged anytime soon.

"Chris just finalized his divorce from Anna [Faris] a couple months ago, and he’s happy with just dating Katherine for now. The couple has a lot of fun together and is fully involved in one another’s life," the source shared, adding that they are "in a committed relationship. There just isn’t a rush to take it to the next step right now. Chris is enjoying the dating process."

While they have remained out of the public eye, they have been spotted attending church, going to dinners and even hanging out with Schwarzenegger's famous father, Arnold, and brother, Patrick.

For more on their romance, watch below.