The “Big Little Lies” star celebrated her look-a-like daughter Ava’s birthday with a heartfelt Instagram post on Wednesday.

“Wow! How is it possible that this little girl is now 21 years old? Happy Birthday to my sweet girl who has become the most incredible young woman,” Witherspoon, 44, wrote alongside a sweet photo of the two of them. “Her kindness, her compassion, and her huge heart never cease to amaze me. Ava, there aren’t enough words to describe how proud I am of everything you’ve already accomplished. I cannot wait to see ALL the Good you will put into this world. I love you so much @avaphillippe 💗”

She also included a black-and-white photo of Ava as a toddler celebrating her birthday.

Ava commented, “love you the most, mama! 🥺💕”

The Oscar winner shares Ava and son Deacon, 16, with ex-husband Ryan Phillippe, 45. She went on to marry talent agent Jim Toth, 50, in 2011 and they are parents to 7-year-old son Tennessee.