Kevin Costner's Next Movie: Everything to Know About Horizon: An American Saga

Kevin Costner has an epic multi-film Western project in the works.

The Oscar-winning actor/director is working on Horizon: An American Saga, which is said to be a saga spanning at least three movies with Warner Bros. Pictures and New Line. As he told PEOPLE in November 2022, the endeavor is "incredibly meaningful to me." He is producing through his Territory Pictures company, and he co-wrote it with Jon Baird.

"It's really been the hardest thing I've ever done, but it's exactly what I want to do," he said at the time.

Costner has portrayed powerful Montana patriarch John Dutton on Yellowstone since 2018, and in February 2023, Deadline reported that the star was hoping to scale back his time on the show in order to focus more of his attention on Horizon.

On Wednesday Entertainment Tonight reported that Costner is not returning to the series after season 5, citing sources. Paramount Network has not commented on the rumors.

Read on for everything we know so far about Horizon.

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What is Horizon about?

The plot is mostly unknown, though a synopsis listed on IMDb says that the film "chronicles a multi-faceted, 15-year span of pre-and post-Civil War expansion and settlement of the American west."

Costner teased to PEOPLE in November 2022 that he has long been drawn to stories about the Wild West.

"A lot of times we measure ourselves against other generations," he said. "I think about what was at stake. How did people survive? There's a rawness and an unpredictability about it. I'm haunted by that."

Who's in the Horizon cast?

Costner, in addition to directing, will star in Horizon. And his teenage son Hayes also has a role in the film.

Costner told PEOPLE in November 2022 of his son's part, "He's very good. Hayes plays the namesake character that I actually play in the movie. He's 13 years old and the screenplay's been around longer than that."

The star shares Hayes, plus Cayden and Grace, with Christine Baumgartner, who filed for divorce in May 2023 after 18 years of marriage. (Costner is also dad to Annie, Lily, Joe and Liam from previous relationships.)

He said of casting his son, "I kind of did it on purpose, so he could be hanging out with me. And the same thing for Cayden, same thing for Grace. I'm like any other parent, I'm trying to figure out, like, 'This is really neat. You should come be with me.' "

The Horizon ensemble cast also includes Sienna Miller, Sam Worthington, Jamie Campbell Bower, Luke Wilson, Thomas Haden Church, Michael Rooker, Jena Malone, Isabelle Fuhrman, Alejandro Edda, Tatanka Means, Tom Payne, Abbey Lee, Wasé Chief, Tim Guinee, Michael Angarano, Colin Cunningham, Scott Haze, Angus Macfadyen, Douglas Smith and Jon Beavers, Deadline reported in September 2022.

The same outlet reported in April 2023 that the second Horizon film will also star Glynn Turman, Kathleen Quinlan and Giovanni Ribisi alongside returning cast members.

Who directed Horizon?

Costner co-wrote and will direct Horizon in addition to starring in it. It's his first time directing since 2003's Open Range. He also directed 1997's The Postman and 1990's Dances with Wolves, for which he won Best Director and Best Picture Oscars. (He was also nominated for Best Actor.)

"Horizon is incredibly meaningful to me. It's really been the hardest thing I've ever done, but it's exactly what I want to do," Costner told PEOPLE in November 2022. "I wrapped this first one, and it took everything I had, but I'm holding on to the rope and not letting go."

He added, "In my career I've tried to choose not based on what was popular. I made the films I wanted to make."

Is there a Horizon trailer?

Warner Bros. Pictures shared an initial teaser trailer for Horizon: An American Saga on Oct. 5, 2023. The 42-seconds-long trailer shared only a minimal glimpse at the new film and shows Costner's character riding a horse and firing a rifle while in the saddle.

When does Horizon premiere?

The first Horizon movie releases in theaters on June 28, with a sequel, titled Chapter 2, to follow soon after on August 16. Costner has said the series will feature two additional movies that have yet to be filmed.