Ethan Hawke makes his debut as a series creator with Showtime’s Civil War-era miniseries “The Good Lord Bird.”

“It was definitely the most challenging undertaking of my life,” says Hawke, 49, who stars in and executive-produced the show. “It was like doing four or five indie movies back-to-back.”

Premiering Oct. 4 at 9 p.m. — and based on James McBride’s National Book Award-winning 2013 novel of the same name — “The Good Lord Bird” follows newly freed young slave Henry, nicknamed “Onion” (Joshua Caleb Johnson), who ends up with famous abolitionist John Brown (Hawke) and his band of soldiers on a crusade to end slavery. It culminates in the 1859 raid on the Army depot at Harpers Ferry, Va. — the prelude to the Civil War.

(Brown ultimately became the first person in US history to be executed for treason; his 1859 hanging is the show’s attention-grabbing opening.)

“I’m not playing John Brown the historical figure, I’m playing John Brown as Onion sees him and as James McBride spins a big yarn,” says Hawke.

Ethan Hawke as John Brown in "The Good Lord Bird."
Ethan Hawke as John Brown in “The Good Lord Bird.”Kevin Lynch/SHOWTIME

“It’s a strange tone to walk. It’s a tone [Quentin] Tarantino has hit and the Coen brothers have hit, where it’s half-ridiculous and half-blistering and half-electric and half-silly and half-preposterous. That was the joy of it — it’s like taking a high dive. You don’t really know how it’s going to go, you just have to throw yourself off and hope you live.”

“The Good Lord Bird” mixes fact and fiction: “All of this is true. Most of it happened,” reads a tongue-in-cheek on-screen announcement. In addition to Brown, the fictional Onion encounters iconic figures such as Frederick Douglass (“Hamilton” star Daveed Diggs).

“I’m a big Mark Twain fan, and I just felt like McBride lapped Mark Twain,” says Hawke. “It’s like [‘The Adventures of Huckleberry Finn’], but Huck Finn flirts with talking about race in America, and McBride dives all-in. So I just wanted to share it with everybody I knew, and the way to do that is to perform it.

Beau Knapp as Owen Brown, Ethan Hawke as John Brown, Joshua Caleb Johnson as Onion, Ellar Coltrane as Salmon Brown and Mo Brings Plenty as Ottawa Jones in "The Good Lord Bird."
Beau Knapp as Owen Brown, Ethan Hawke as John Brown, Joshua Caleb Johnson as Onion, Ellar Coltrane as Salmon Brown and Mo Brings Plenty as Ottawa Jones in “The Good Lord Bird.”William Gray/SHOWTIME

“The Harpers Ferry raid is one of the most dramatic events in US history, and I couldn’t believe it hasn’t been 15 movies,” he says. “They made about a hundred movies about the Alamo…[the raid] is such an incendiary story, and to talk about it forces you to have other conversations that are hard. That’s why it’s been avoided.”

The seven-episode miniseries is a rare TV role for Hawke, whose career has primarily been on the big screen, where he’s racked up four Oscar nominations to date (“Best Supporting Actor” nods for “Boyhood” and “Training Day” and “Best Adapted Screenplay” nods for “Before Sunset” and “Before Midnight”).

He says, though, that creating a TV series has not been a longtime ambition.

Joshua Caleb Johnson as Onion and Ethan Hawke as John Brown.
Joshua Caleb Johnson as Onion and Ethan Hawke as John Brown.Kevin Lynch/SHOWTIME

“It was really just this story. I was thinking, ‘How would you tell that book in two hours?’ You wouldn’t be able to reduce it enough for a movie,” he says. “And my wife [producer Ryan Hawke] was like, ‘Dummy, there’s this thing called limited series now, wake up!’ So in a lot of ways, I always just thought of it as a long movie.”

But despite the massive undertaking by Hawke to co-create “The Good Lord Bird” — along with “Hell on Wheels” writer Mark Richard — and to executive-produce the series, he says it wasn’t a hardship to star in it as well.

“I love acting. I loved being on set with the guys and playing this character,” he says. “In a lot of ways, the production was the work, and the work was the play.

“Gene Hackman has my favorite line: ‘They pay me to wait. I’ll act for free. It’s the waiting I hate.’ ”