Prince Harry and Meghan Markle joined "Yellowstone" star Kevin Costner at his A-list charity event.

The Duke and Duchess of Sussex joined Hollywood royalty at Costner’s One805 Live! fundraiser at his $26 million estate in Santa Barbara.

Other celebrity guest appearances at the star-studded event included Oprah Winfrey, and Maroon 5 headlined the fall fundraiser that honored the first responder community. 

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Prince Harry Meghan Markle charity event

Prince Harry and Meghan Markle joined "Yellowstone" star Kevin Costner at his A-list charity event. (Backgrid)

The glitzy charity event raised money to provide financial aid and mental health support to first responders. 

Costner, an ambassador of One805, was onstage with Harry and Markle as they made a surprise appearance to present him an award. 

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The "Suits" actress wore a stylish monochrome jacket with her hair pulled back in a low bun. Markle completed her look with gold earrings and a matching watch.

Harry sported a casual black shirt and blazer as the two supported their celebrity friend Costner. 

Prince Harry Kevin Costner

Kevin Costner, an ambassador of One805, onstage with Prince Harry and Meghan Markle as they made a surprise appearance to present him with an award.  (Backgrid)

"Good afternoon everyone," Costner greeted the crowd after he received his award. "Now, I get asked a lot by my friends who have no manners, ‘Kev, what’s this place cost? What’s it worth?’ And I can just simply tell you on a day like today it’s worth every penny.

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Maroon 5

Maroon 5 headlined the fall fundraiser honoring the first responder community. (Instagram/One805)

"That you’ll be here to celebrate people you’ll never maybe meet," he continued. "The ones who are the first to rush in. And it's a place that I’ve had a lot of good luck in my life, and I’ve tried to not throw up a wall around it. So, thank you for coming."

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In another video shared by One805's Instagram account, Oprah praised the charity and highlighted the work of the first responders. 

Costner hosted the event shortly after he settled his divorce with ex-wife Christine Baumgartner after 18 years of marriage. 

Oprah Winfrey

Oprah Winfrey (Instagram/One805)

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Baumgartner filed for divorce May, 1 citing irreconcilable differences. In documents obtained by Fox News Digital, she listed April 11 as their date of separation.

Meanwhile, Harry and Markle recently returned from the Invictus Games in Germany

The couple celebrated the Duke of Sussex's 39th birthday at his charity event overseas. 

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Harry created the Invictus Games in 2014 for wounded, injured and sick military service members.