Reese Witherspoon and Ryan Phillippe
The Cruel Intentions co-stars married in 1998 before they started filming, but as one of our favorite movie star couples of all time, they had to be included. After having two children, they divorced in 2007, and Reese went on to date her Rendition co-star Jake Gyllenhaal. Ryan moved on with his Stop-Loss co-star Abbie Cornish, whom he reportedly romanced while still married to Reese.
Neither are currently with fellow actors, but Reese recently married and had a baby with talent agent Jim Toth!