The "Mr. & Mrs. Smith" co-stars have been together for about six years.
One insider told the magazine Jolie and Pitt plan to exchange vows in an "intimate and informal" ceremony.
Pitt told USA Today in May their children have been pressuring them to get married.
"The kids ask about marriage," Pitt told the newspaper. "It's meaning more and more to them."
2014: The Year in Music [PHOTOS]