"Sometimes relationships just run their course," an unnamed source has told the New York Post, confirming the split.
The Australian actor and country music singer have been living apart since June, according to entertainment website TMZ.
As recently as June, Kidman shared a photo of herself cuddled up to Urban on instagram to commemorate their wedding anniversary.
It is believed Urban, 58, has moved out of the couple's Nashville home, and reports say Kidman is desperate to save the relationship.
"She didn't want this," another unnamed source told People magazine. "She has been fighting to save the marriage."
The duo share two children, Sunday Rose, 17, and Faith Margaret, 14.
They married on June 25, 2006, nearly a year after first meeting at the G'Day USA gala in January 2005.
Kidman was previously married to Tom Cruise from 1990 to 2001. She and the Top Gun actor share two kids: Bella, 32, and Connor, 30.
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