Jessica Simpson is kissing her 30s goodbye.

The star took to Instagram on Friday to share a photo of herself rocking a new cow-print bikini from her Jessica Simpson Collection swimwear line.

The 39-year-old fashion designer and singer paired the look with a black, sheer cover-up featuring lace embroidery and a black hat with gold embellishments.

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"YEE-HAW to my final days in my 30’s," Simpson captioned the snapshot, which featured the mom of three looking back at the camera.

The "Open Book" author's label also shared a photograph of the star modeling the new two-piece as she posed on the beach.

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"Cancer Season! ✨ 🌟💫 New summer swim is now on jessicasimpson.com! 📸 @kristingram #JessicaSimpsonStyle #JessicaSimpsonSwim," the caption reads.

Simpson's birthday is on July 10.

Last month, Simpson shared another photo of herself wearing a look from her collection -- this time, workout shorts and a matching sports bra.

In the picture, Simpson was drenched in sweat after an early morning workout session as she flexed her leg muscles, showing off her incredibly toned calves.

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"Woke up before all 3 kiddos to get my steps in and spend time with me, myself, and I. Move move move for your own mental health. 💪🏻" she captioned the photo.

Jessica Simpson signs copies of her new book 'Open Book' at Barnes & Noble Union Square on February 04, 2020, in New York City. 

Jessica Simpson signs copies of her new book 'Open Book' at Barnes & Noble Union Square on February 04, 2020, in New York City.  (Kevin Mazur/Getty Images)

In 2019, Simpson revealed her dramatic 100-pound weight loss after the star gave birth to daughter Birdie Mae.

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Her trainer, Harley Pasternak, revealed last fall that Simpson's fit body is the result of her dedication to a more holistic post-baby lifestyle.

Fox News' Melissa Roberto contributed to this report