Derek Jeter & Hannah Davis: MARRIED!!

Derek Jeter and Hannah Davis are MARRIED ... tying the knot tonight in front of friends and family at a Napa Valley resort!!

Jeter, 42, married Davis, 26, at the Meadowood Napa Valley Resort in St. Helena, California. People first reported the wedding.

Davis -- who's a Sports Illustrated model -- wore a custom made dress designed by Vera Wang.

The couple dated for almost 4 years before getting hitched.

Congrats!!