The proposal – of course – happened Saturday on the dance floor during a performance of Sway at the Olympia Theater in Miami, in front of a joyous audience and a line of other dancers.
Chmerkovskiy, 35, told her, "I'm in love with you, and I will be in love with you for the rest of my life."
Then: "She said 'yes,' " he posted on Instagram later that night.
Maks & Val Chmerkovskiy Wear Nothing But Hats. (And Not on Their Heads!)
"Maks' romantic proposal is something I will cherish for the rest of my life," Murgatroyd said in a statement to PEOPLE. "I'm excited for the next chapter in our lives and to plan the wedding of my dreams with Maks."
Chmerkovskiy popped the question with a custom-designed Cantamessa ring.
The DWTS favorites have been on and off since 2012, though a source told PEOPLE in January, of Chmerkovskiy and Murgatroyd, 29, that "Peta is his girl and he's never stopped wanting to be around her."
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Their friends and family couldn't be happier with the engagement.
""So this just happened!!!! Ahhhhh I'm so excited for my loves!! @maksimc and @petamurgatroyd it's about bloody time!!!!" DWTS' Sharna Burgess wrote on Instagram. "Congratulations you two!!! #iwishiwasthere #madeforeachother."
Chmerkovskiy's brother Val also took to Instagram, writing, "I love the two of you with all my heart. you have my brothers loyalty, heart. his one and only for the rest of his life. you're family now and that makes you my sister, the second most important woman in my life.
"What's mine is yours. Forever and always. Petachka your team got numbers now."
With reporting by PATRICK GOMEZ