The 33-year-old actress and 29-year-old actor were together four years, and share three-year-old daughter Marlowe. The former couple were last seen together in Ibiza, Spain earlier this month.
"Tom and Sienna split a few weeks ago, but still love and respect each other as friends and parents," a source told The Sun. "It's a very amicable breakup and they intend to remain great friends."
"They were in a bit of a rough patch for a while. Their schedules, on top of raising a child, started to get to them," an insider shared with Us Weekly. "It seemed like it was only a matter of time," a source added to E! News.
Miller was previously engaged to actor Jude Law, and started dating Sturridge in 2011. She and Sturridge appeared in a Burberry ad campaign together in 2013, but kept details about their relationship tightly under wraps.
Miller is scheduled for a number of upcoming projects, including adaptations of Hippie Hippie Shake, The Lost City of Z and High Rise, and new Ben Affleck-directed film Live by Night. Sturridge will star as Henry VI in an upcoming BBC adaptation of the William Shakespeare play.