Reedus, 49, shared a photo of the two wearing face masks. "Happy Birthday sunshine," Reedus wrote in the caption.
Kruger also shared the Zodiac message for her birthday.
"What you accomplish in the world at large always begin with an idea in your head and some of the ideas you come up with this year will be touched by genius," the message reads. "Your higher mind and your human mind are now in perfect alignment."
"I’m just gonna go with this one and hope for the best," Kruger added in the caption.
Reedus and Kruger reportedly started dating in late 2016, although they met the year before when they made the romantic drama Sky together. The two took their relationship public in March 2017, then made their red carpet debut at the 2018 Golden Globe Awards in January.
In May, sources said the two were expecting their first child together. According to PEOPLE, Kruger sparked pregnancy speculation when she wore loose-fitting outfits to the 2018 Cannes Film Festival.
This will be Kruger's first child. The German actress was previously married to Guillaume Canet from 2001 to 2006, and had a 10-year relationship with The Affair star Joshua Jackson until 2016. Coincidentally, Jackson also appeared in Sky, which is available to stream on Netflix.
As for Reedus, he was previously in a relationship with model Helena Christensen from 1998 to 2003. The couple have an 18-year-old son, Mingus Lucien Reedus.
In Sky, Kruger starred as a woman who escapes an abusive husband while on vacation in California. When she reaches Las Vegas, she meets Reedus' character and they start a romantic relationship.
“I didn’t know [Reedus] before the film,” Kruger told PEOPLE in April 2016. "We share a lot of intimate scenes... I was really nervous about meeting him and not being able to have a drink with him, or talk with him.”
Kruger said she was "pleasantly surprised" by Reedus' off-screen personality, which is nothing like the characters he plays on the screen.
"She's a dream," Reedus said of Kruger in 2016.
Kruger also said Reedus "guilt-tripped" her into catching up on The Walking Dead.0comments
Reedus is best known for playing Darryl Dixon on The Walking Dead, which will return for a ninth season later this year. Kruger's next movie is Welcome to Marwen, which opens on Nov. 21.
Photo credit: Axelle/Bauer-Griffin/FilmMagic