Christine Baumgartner and Kevin Costner are divorcing after 18 years of marriage. Photo / Getty Images

After 18 years of marriage, Kevin Costner’s wife, Christine Baumgartner, has filed for divorce, citing “irreconcilable differences”.

According to the Daily Mail, the pair began dating in 2000 and tied the knot in 2004 at Costner’s Colorado ranch.

But 49-year-old Baumgartner, a model and fashion designer, is understood to have pulled the pin on the marriage and is seeking joint custody of their three children - Cayden, 15, Hayes, 14, and Grace, 12.

Costner, 68, has filed a response and is said to also be seeking joint custody.

A statement has been issued from the Yellowstone star’s rep: “It is with great sadness that circumstances beyond his control have transpired which have resulted in Mr Costner having to participate in a dissolution of marriage action.

“We ask that his, Christine’s and their children’s privacy be respected as they navigate this difficult time,” the statement concluded.

It is alleged Baumgartner is not filing for spousal support and based on a response from Costner filed by lawyer Laura Wasser, it is understood a pre-nuptial agreement was made between the pair.

“Spousal support to be payable to petitioner pursuant to the terms of the parties’ Premarital Agreement,” it said.

Costner, who became a household name after starring in the 1992 Whitney Houston blockbuster The Bodyguard, was married with children before meeting Baumgartner.

From 1978 to 1994 he was married to Cindy Silva and had three children, Annie, 39, Lily, 36, and Joe, 35.

After his divorce from Silva, he was in a relationship with Bridget Rooney and the pair had a son, Liam.

Amid news of Costner’s divorce, the Hollywood legend is also rumoured to have had trouble on the set of his hit series Yellowstone.

According to the Daily Mail, the show’s fifth season will be its last due to ongoing friction between Costner and the show’s creator Taylor Sheridan.

A source close to the production team told the Daily Mail Sheridan had developed a “god complex” on set and told Costner, also an executive producer on the show, to “stick to acting” when he raised concerns about the direction of the series.