There has been no official comment from representatives of the couple, but a source told the Sun: "Tom and Sienna split a few weeks ago but still love and respect each other as friends and parents. It's a very amicable break-up and they intend to remain great friends."
The couple seemed very much still an item when they were last seen together on a family holiday with their daughter in Ibiza at the beginning of July.
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Sienna Miller and Tom Sturridge have reportedly split
Sienna first sparked split rumours when she was seen without her engagement ring at Cannes Film Festival, however a rep later explained that it was not an "appropriate" piece of jewellery for her outfits.
The 33-year-old was once again seen without her engagement ring when she attended Wimbledon on Friday. Despite the break-up reports, Sienna appeared in high spirits as she chatted with talent agent Ari Emanuel and 12 Years a Slave actor Chiwetel Ejiofor.
Sienna and Tom began dating in 2011 and got engaged the following year after announcing they were expecting their first child together. The couple often supported each other at high profile red carpet events including the Oscars and each other's film premieres.
Sienna was seen without her engagement ring at Wimbledon
The attractive pair even starred in Burberry's autumn/winter 2013-2014 ad campaign, where they shared a kiss to mark their first professional shoot together as a couple.
Sienna had nothing but positive words about the actor, telling Esquire in 2014: "He's the perfect balance to my lunacy, which makes him sound really boring but he's not, at all."
The American Sniper star was previously engaged to actor Jude Law before they parted ways in 2006.