The 46-year-old Trainspotting star and the 33 year old British actress first sparked rumours of a romance when they were spotted kissing last year, just months after ending his 22 year marriage to Eve Mavrakis, 51.
According to US magazine Star, Mary dumped Ewan as she “hated being labelled a home wrecker and the embarrassment it caused her.”
"It’s sad because a year ago Ewan and his wife were in great shape and then he decided to throw it all away for Mary.
"Now it looks like he’s lost them both for good."
Ewan, who shares four children with production designer Eve, was believed to have cited irreconcilable differences when he filed for divorce last month.
Speaking to The Sun in January, Eve said of the marriage break down: It’s disappointing and upsetting but my main concern is our four children are OK
Ewan caused a stir at the golden Globes last month, thanking both his wife and new firfriend in his acceptance speech.
“I want to take a moment to thank Ev, who always stood beside me for 22 years and my four children, I love you,” he said.
“I’ve always loved being an actor and hanging out with actors and I got amazing actors to work with on this and it wouldn’t be any Emmett or Stassi without David, Michael, Carrie Coon and there would be no Rey without Mary Elizabeth Winstead so thank you very much.”