The Big Bang Theory actress, 38, announced she was engaged to her actor fiancé Tom Pelphrey, 42, in a series of Instagram posts on Wednesday - one of which showed her stroking her partner's face while showing off her new bling.
Hours later, she posted a video of her engagement ring, giving fans a close-up look at the sparkler.
She said in a caption it was a "once-in-a-lifetime slice of perfection", adding: "My heart can't take it!"
Cuoco added: "What a wild, beautiful journey life can be. Grateful for every road that led me straight to you."
Pelphrey popped the question with a gold band boasting a main oval diamond flanked by smaller stones.
Cuoco also revealed he collaborated on the design of her ring with jeweller Shahla Karimi, whose designs have been worn by Hailey Bieber and Taylor Swift.
The actress was previously married to tennis player Ryan Sweeting from 2013 to 2016 and Karl Cook from 2018 to 2022.
She captioned a series of images of herself flashing her engagement ring from Tom that she posted on her Instagram Stories: "Amazing weekend."
Other images in her carousel of snaps announcing her engagement included photos of her and Ozark actor Pelphrey hugging the actress' first child - daughter Matilda Carmine Richie, who she had with her now-fiancé in 2023.
Cuoco recently opened up about leaving behind hectic Hollywood for a quiet life on her ranch in Thousand Oaks, California.
She told People: "I wanted something away from LA. I love being an actor and I love the business, I really do, I've been in it my whole life.
"I know nothing else for 30-plus years. But I knew I needed a special place that wasn't that and that felt more grounded, felt more real, felt more family-oriented because I do love that side of my life, but this is equally as important to me."
Cuoco bought her ranch for $US6.4 million ($A9.7 million) in 2023 not long after it was built, and she added to People about falling in love with the idea of living in the home: "I was like, 'I want my own ranch. I want my own place.'
"And I wanted a place for my family. My family's family and my child and my brain."
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