The 37-year-old singer and former "The Voice" coach marked the occasion by dedicating a sweet post to Matthew Rutler on Instagram.
Aguilera shared a black and white photo of herself embracing Rutler. The couple got engaged in February 2014 after more than three years of dating.
"Birthday boy ...to a wonderful father, loving man and hardest worker I know," Aguilera captioned the post, adding a blue heart emoji.
Aguilera shares 3-year-old daughter Summer Rain with Rutler, and is also mom to 10-year-old son Max Liron. Rutler posted a video Thursday on Instagram Stories of Summer presenting him with a birthday gift.
"Best birthday gift ever," he wrote.
Aguilera said in an interview with People in 2015 that she and Rutler are "not in a rush" to marry.
"I want to plan it and cherish the moment, while not feeling rushed," the star explained.
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"Our love is secure enough that we don't need a wedding to prove our love or commitment," she said. "We are enjoying our daughter, our family and our work for now."
Aguilera is instead focusing on her new studio album. The singer, who last released the album Lotus in 2012, told fans in January that her new album is "coming."
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