Last year, ahead of the release of By The Sea, the romantic drama the couple both star in, Jolie told The Telegraph: "Brad and I have our issues.
"We have fights and problems like any other couple. We have days when we drive each other absolutely mad and want space, but the problems in the movie aren't our specific problems."
Jolie will reportedly be represented by lawyer Laura Wasser, whose previous clients include Johnny Depp, Kim Kardashian, Stevie Wonder and Britney Spears.
Pitt and Jolie: A history
Jolie and Pitt - nicknamed "Brangelina" by fans - are one of the best-known couples in Hollywood.
They got together after meeting on the set of the film Mr & Mrs Smith, which was released in 2005.
Jolie, who is the daughter of actor Jon Voight and actress Marcheline Bertrand, rose to fame with roles in films such as The Bone Collector and Girl, Interrupted, for which she won a best supporting actress Oscar in 1999.
She starred as Lara Croft in the Tomb Raider film series and went on to appear in Changeling, Salt, A Mighty Heart, Wanted and Maleficent.
She also directed World War Two prisoner of war film Unbroken.
Pitt's early acting roles include appearing alongside Susan Sarandon and Geena Davis in Thelma and Louise.
He went on to appear in films including Fight Club, Ocean's Eleven, World War Z, Snatch and The Curious Case of Benjamin Button.
His producing work includes 12 Years A Slave, which won a best picture Oscar in 2014 and The Big Short, in which he also acted.
Pitt and Jolie most recently worked together on 2015 film By The Sea - a relationship drama written, directed and produced by Jolie.