The actress is at the beach, showing off the ring - and her white nail polish. According to People, the elongated radian cut ring is 4 carats, and was personally designed by Zandy along with Leor Yerushalmi and The Jewelers of Las Vegas.
In the photo, Lea is covering her face with her left hand, allowing the sparkling piece of jewelry to take center stage.
Lea previously opened up to People about her life with 32-year-old Zandy, "I'm very happy and I think that you can tell".
The couple have been dating for just under a year.
Lea and Zandy were first romantically linked in July 2017.
Lea Michele and Zandy Reich have not announced if they have chosen a date yet for a wedding.
The duo have kept the relationship relatively under wraps with Reich appearing in only a handful of Lea's Instagram photos in recent months.
From Lea's previous social media posts, it's been clear that she and Zandy have something special.
Canadian actor Monteith, who played school jock Finn Hudson in Glee, was found dead in a Vancouver hotel room in 2013, aged 31.
Before that, she romanced personal trainer Matthew Paetz for two years until 2016.