Back in April, Phillippe gushed over his gorgeous girlfriend during a sit-down with Howard Stern.
"She's awesome. When people see her they have these judgments because she could be a model, but she's about to graduate Stanford Law," he shared. "Also what's great about it -- as you get older certain issues become more important to you. I'm very involved in civil rights issues, and so to be with a woman who could actually make an impact in the legal realm -- that's a beautiful thing."
Phillippe was previously married to his Cruel Intentions co-star Reese Witherspoon from 1999 to 2007. The pair share two children -- 16-year-old daughter Ava and 12-year-old son Deacon. Phillippe is also father to a 4-year-old daughter, Kai, who he shares with ex-girlfriend Alexis Knapp.
Later this week, Phillippe and Slagter are slated to make an appearance at the Five Star New Year's Eve party on Watson Island in Miami, where fans might get a peek at the Stanford law student's new ring.
ET has reached out to Phillippe's rep for comment.