Justin Verlander put a ring on it ... a MASSIVE ring ... and Kate Upton was all about showing it off at the Met Gala in NYC.
Upton hit the red carpet at the event Monday night sporting the boulder on her finger ... and essentially stole the show from all the other huge stars at the event.
Don't worry, Justin can afford it ... he signed a $180 MILLION contract in 2013.
FYI, Upton started dating the Detroit Tigers pitcher roughly 3 years ago ... and they've been inseparable ever since.