Chmerkovskiy, 35, proposed to Murgatroyd, 29, on Saturday on the dance floor during a performance at the Olympia Theater in Miami, FL, Peoplereported.
The couple got engaged in front of a live audience and many other dancers who were onstage.
Chmerkovskiy reportedly told her, "I'm in love with you, and I will be in love with you for the rest of my life," and presented a custom-designed Cantamessa ring.
Murgatroyd replied, "Yes."
"Maks' romantic proposal is something I will cherish for the rest of my life," Murgatroyd said in a statement obtained by People. "I'm excited for the next chapter in our lives and to plan the wedding of my dreams with Maks."
The couple had an on-again, off-again relationship beginning in 2012, and both individuals dated other people when they had called it quits. They reportedly split a couple of weeks before Valentine's Day in 2013 but rekindled their romance for good this past January.
"Peta is his girl and he's never stopped wanting to be around her," a source told the magazine.
"She is so the opposite of clingy and is content to just spend time with him and be happy," the source said.
"So this just happened!!!! Ahhhhh I'm so excited for my loves!! @maksimc and @petamurgatroyd it's about bloody time!!!!" DWTS pro Sharna Burgessposted on Instagram. "Congratulations you two!!! #iwishiwasthere #madeforeachother."
Chmerkovskiy's brother Val Chmerkovskiy also wrote on Instagram: "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."
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Chmerkovskiy and Murgatroyd were spotted holding hands and smiling ear to ear one day after he had popped the question.
Chmerkovskiy leftDancing with the Stars after winning the show's eighteenth season with Olympic ice dancer Meryl Davis. Murgatroyd had to sit out the most recent edition of the show due to injury, but she made it known she was extremely disappointed not to compete.