While the couple never officially announced they were engaged, the 26-year-old actress sparked rumours when she stepped out at The Legend of Tarzan premiere while wearing a massive, pink, cushion-cut, halo diamond ring on that finger.
The couple met in 2013 on the set of Suite Française where Tom worked as an assistant director.
"I was the ultimate single gal. The idea of relationships made me want to vomit," she said. "And then this crept up on me," she told US Vogue back in May.
"We were friends for so long," she said. "I was always in love with him, but I thought, 'Oh, he would never love me back. Don't make it weird, Margot. Don't be stupid and tell him that you like him.' And then it happened, and I was like, 'Of course we're together. This makes so much sense, the way nothing has ever made sense before.'"