UsWeekly.com reports the E! “Fashion Police” co-host, 28, and Mosshart, a chef, 29, quietly got engaged just a few weeks before Christmas.
The pair is "really excited" about taking the next step in their relationship, a source told Us. "Kelly is the happiest she's ever been. Her career is going well, and she's in a healthy relationship with a wonderful guy."
Osbourne and Mosshart having been dating for over a year after meeting at friend Kate Moss' wedding in July 2011.