McCary posted a photo of the two of them showing off Stone’s new ring, captioning the photo with heart emojis.
Stone and McCary, who have been dating for two years, have been very quiet about their relationship.
They met when Stone hosted SNL in 2016.
In April, the 31-year-old actress posted a photo of herself, McCary and Bradley Cooper at the 25th annual Screen Actors Guild Awards at The Shrine Auditorium from Jan. 27 on Instagram.
Stone’s fans celebrated the news of her engagement on Twitter.