The pair, together since 2005, has six children together: Maddox, 13, Pax, 10, Zahara, 9, Shiloh, 8, and twins Knox and Vivienne, 6.
Pitt, 50, and Jolie, 39, vowed not to marry until all Americans were allowed to do so and became engaged in April 2012 at the request of their children.
"It [marriage] seems to mean more and more to our kids," Pitt told the Hollywood Reporter in January 2012. "We made this declaration some time ago that we weren't going to do it 'til everyone can. But I don't think we'll be able to hold out."
Pitt collaborated with jewelry designer Robert Procop in creating a custom engagement ring for Jolie.