The Voice coach marked the very special occasion on Thursday and her longtime love, Blake Shelton, found the sweetest way to share his affection.
"Happy Birthday @gwenstefani !!!! I love you so much it's actually stupid... And possibly illegal in the state of California," he quipped on Twitter.
But the 43-year-old's touching message is just one of his plans for Stefani's birthday. A source tells ET that the fellow Voice coach has taken her on a vacation. He "wants to make her feel special." And when they get back, he is putting together a seasonal shindig to honor the momentous b-day.
Happy Birthday @gwenstefani!!!! I love you so much it’s actually stupid... And possibly illegal in the state of California.
"Gwen is turning 50 and she's over the moon about it. She feels confident in her age and she is completely in love," the source shares. "Blake wants to make her feel special. He's planning a big party for her, he is going all out! It's a costume party. Gwen is a huge costume lover. She has always loved dressing up for Halloween."
Diehard fans know that this couple loves All Hallow's Eve. Last year, Stefani dressed up as Sally, the undead beauty from The Nightmare Before Christmas and Shelton sported a vintage sailor suit for someone else's party. The source adds that the songstress and her boyfriend are totally enamored with each other as they gear up to celebrate her birthday.
"Blake and Gwen have a lot to celebrate. They are both so incredibly happy in their relationship and in their lives right now. They have full open communication and truly appreciate one another. Gwen is always saying she has found her soulmate and best friend," the source states.
In January, ET spoke with Stefani about her eyewear collection, where she shared her reaction to the upcoming milestone birthday. "I feel the same as I always feel, which is horrified," she candidly said. "Nobody wants to grow older. But, you know, I feel like I’m also in an amazing place in my life. I feel so blessed right now."
Gwen Stefani and Blake Shelton Looked 'Very Much in Love' at Church With Her Kids (Exclusive)
"I always knew at this point in my life I was going to be turning this age, which is hard to even say out loud, but where I would be with my kids and what place they would be at and I feel so, like, I’m in a good balance of being able to work and also be here a lot and enjoy being a mom and being there for them," Stefani continued. "It’s exhausting but, you know, being able to design and be at home and also be creative and also be a good parent as best as I can be -- it’s inspiring. It’s a good time in my life. I mean, I cannot complain."
Before the premiere of season 17 of The Voice last month, ET spoke with Shelton about his girlfriend returning to the show as a coach for the first time since season 12, noting that he's typically more competitive than her.
"You know, she wants to win and I want to win and that's what they pay us to do on this show is to try to win the show," he said. "It's harder for [Gwen]. She's not, she's not competitive. She'll be the first to tell you right up until it gets competitive and then all of a sudden she is."
He also gushed: "I couldn't be happier that she's back on the show."
See more from Shelton's interview in the clip below.
Reporting by Adriane Schwartz
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