The engagement ring in question is a trinity diamond - a large diamond which sits between two smaller yet identically cut stones - and has a gold band. The La La Land star has kept the details of her relationship low-profile, with few sightings out and about and even less known about their possible engagement, which was first reported by OK! Magazine in December.
The Oscar winner wore a light gray coat, a black cap, jeans, and a pair of Mansur Gavriel mules, the 30-year-old flashed the sparkle while clutching her wallet - giving fans the first look at her engagement ring.
Emma Stone previously dated Andrew Garfield from April 2011 until sometime around October 2015. While the low-key couple never publically confirmed their split, Emma touched on the subject briefly during an interview with Vogue, saying: "It's been a good year. And sad. Pros and cons." She adds that Andrew is "someone I still love very much".