"It's a recent engagement. They're just two people who found love quickly and make each other happy all the time. They both started talking about it this past weekend. It's nothing they've been hiding," a source close to the couple told people.com.
Grande tweeted an emoji-filled message moments after the news went public on Monday.
"I love you," she wrote, flanked by laughing monkey faces. She continued by writing "sm" (presumably "so much") before adding more monkey faces and signing off with "ok bye".
The pair, who began dating shortly after Grande's breakup from rapper Mac Miller in May, have been using social media to express their affection for one another.
Davidson confirmed he had split from his longtime girlfriend Cazzie David in May.
(With IANS Inputs)