The first photo shows grown-up Ava, who is the spitting image of her mother, wearing white and walking on the beach. The second photo shows Ava as a little kid, smiling at the camera and wearing a big red bow.
As Phillippe leaves her teenage years behind, her Oscar-winning mother couldn't help but get a little sentimental with a sweet message on Instagram.
"Watching your little girl grow into a gorgeous, thoughtful, compassionate, fun-loving young woman defies words. It has got to be the greatest gift I could ever receive. I love you @avaphillippe to the moon, around the stars and back! Happy 20th!" Witherspoon wrote.
The mother-daughter look-alikes clearly have a very close bond. Witherspoon, 43, told Ellen DeGeneres in May that she shed a few tears when Ava left for college.
“It’s weird when your children go away to college. It’s hard,” she said. “... I might have gone into her empty room, laid down on her bed and cried when she went to college.”
Ava, who is active on Instagram, even shared a photo of her boyfriend earlier this year, prompting some chatter that her new love looks a lot like a younger version of her father, actor Ryan Phillippe.
“I thought this was a throwback pic of @reesewitherspoon & @ryanphillippe,” one fan commented.