The couple's marriage ended, and both became single, on Friday, nine months after she filed for divorce, a judgment entered on Tuesday in Santa Barbara County court showed.
In the first months after their split, Costner and Baumgartner fought in court over child custody and support payments and appeared to be headed for a contentious trial. But they reached a settlement agreement in September that allowed them to avoid it.
The two will have joint custody of their sons, aged 16 and 15, and daughter, aged 13. A judge in September ordered Costner to pay about $US63,000 ($A96,000) per month in child support, after she had sought about $US175,000 ($A266,000) per month.
Costner, 69, and Baumgartner, 48, a model and handbag designer, began dating in 1998 and married at his Colorado ranch in 2004.
It was the second marriage for Costner, the Oscar and Emmy winning star of TV's Yellowstone and films including Dances With Wolves, The Bodyguard and Bull Durham.
He also has four adult children from previous relationships.
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