Taking to Instagram, the Cry Me A River star paid a heartfelt tribute to the Hollywood star with a series of never-before-seen pictures, including a beautiful snapshot of them on the beach together.
In the caption, Justin wrote: "Happy Birthday to my favorite person in the world... the strongest, funniest, best, brightest and most beautiful mom/partner/BOSS there is.
VIDEO: Justin Timberlake opens up about his family life
"I'm lucky to learn from you and laugh with you and celebrate you every day. But, today we do it with!!!!
"Here’s to more slow-mos in the wind, jumping into bushes to save our kid’s toys, and timing out jump pics perfectly...
"I love U with all that I know."
Jessica Biel and Justin Timberlake on the beach at sunset
Fans were quick to comment on the sweet tribute, with one writing: "This is so sweet!" while another wrote: "What a sweet wife you have." A third added: "Have a great day Jessica."
Jessica will no doubt have a special day with her husband and two young sons, Phineas and Silas.
In January, Justin delighted fans after confirming the name of his second son, who was born in July.
Justin paid tribute to his wife on her birthday
The 39-year-old appeared on The Ellen Show, and gushed about his little boy. "His name is Phineas, and he is awesome and so cute and nobody's sleeping but we are thrilled.
We are thrilled and we couldn't be happier. We are grateful," he said.
Asked how he and Jessica are coping with two children, he joked: "We don't see each other anymore," before adding: "It's a lot of fun, but I guess the saying goes 'Go from a zone defence to a man-to-man very quickly'. It's great, and Silas is very excited. Right now he is very much liking it.
Jessica rescuing one of her children's toys
"Phin can't walk yet or chase him down, so we'll see what happens," he said.
The actor and singer then went on to reveal that his five-year-old is musical, just like him, but he enjoys other hobbies such as "Legos, tennis and we got him a Nintendo Switch... yeah... it's like child crack. Can I say that on daytime TV?"
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