Alan Ritchson, star of the Prime Video crime drama “Reacher,” didn’t expect the show to be an instant hit. 

“When my manager called me on a Saturday and said, ‘You’re buying me an Aston Martin,’ I had some sense that the numbers were good,” Ritchson, 41, told The Post.

“But right away, we couldn’t believe how many people were watching. A lot of people were hopeful, but I don’t think anybody expected that kind of response, so fast.

“I don’t even know if Amazon [expected it], and they probably paid $2 billion for posters,” he joked.

Season 1 of “Reacher” premiered last Feb. 4 and became the first Prime Video series to top Nielsen’s streaming rankings. According to Amazon, “Reacher” is one of the streaming platform’s Top 5 most-watched shows of all time.

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And, ahead of the Dec. 15 Season 2 premiere, it’s already been renewed for a third season.

The action star showed off his strength smashing through a car window in the opening episode.Brooke Palmer/Prime Video

Alan Ritchson in “Reacher” Season 2, which gets into his military roots more.Brooke Palmer/Prime Video
Based on the “Jack Reacher” book series by Lee Child (that was also adapted into the 2012 movie starring Tom Cruise), “Reacher” follows the title character (Ritchson), a hulking, 6-foot-5 drifter and former military policeman who travels around the US using his smarts, skills and brute force to battle various bad guys, get out of dangerous situations and help others (including a mom who’s being carjacked).

“The whole time that we were filming Season 1, I was saying to myself, ‘Please, just be good enough to get a Season 2.’ If we’re good enough for a second season, we’ll be able to stay on for a while,” said Ritchson, also known for “The Hunger Games: Catching Fire,” “Smallville” and “Fast X.” 

“Because of the books, ‘Killing Floor’ [on which Season 1 was based] was good, and I think it was a smart move to open the series on the first book, where we meet the character,” he said. “But, I don’t think it’s the best ‘Reacher’ book. There are some that are so fun, so cinematic, and so made for the medium of streaming, that I can’t wait to get to.”

Ritchson cited “Die Trying” as the book in the series that he’s especially anticipating: “If we were to do that. So, knowing what the potential is for where the show can go, I just wanted to get through the first season and get a pickup. And then, we got the response we did.”

Alan Ritchson as the hulking, 6-foot-5 drifter Reacher, in “Reacher” Season 2.Brooke Palmer/Prime Video

Alan Ritchson said he didn’t expect the show to be such an instant hit.Brooke Palmer/Prime Video
Season 1 found Reacher in the town of Margrave, Ga., where he was arrested for murder and then helped local cops solve a conspiracy involving corrupt local politicians and lawmakers.

In Season 2 (based on the 11th book in the series, “Bad Luck and Trouble”), the members of Reacher’s former US Army unit, the 110th MP Special Investigations, are being mysteriously murdered.

He reunites with three of his former teammates to investigate: Frances Neagley (Maria Sten), forensic accountant Karla Dixon (Serinda Swan) and fast-talking David O’Donnell (Shaun Sipos).

Alan Ritchson said he’d love for the show to get to the book “Die Trying” in the “Reacher” series.Brooke Palmer/Prime Video

Reacher (Alan Ritchson) with his former teammate, Karla (Serinda Swan).Brooke Palmer/Prime Video
Ritchson said he did his own stunts for one of Reacher’s big physical scenes.

“There’s a moment somewhere near the finale, where there was an 8-foot sheet of glass that I had to run through. I wanted to do the stunt, and I’ve never run through a plate of glass before,” he said. “Every alarm in your body starts going off, like, ‘Please don’t do this to yourself!’ And I hulk-smashed right through that glass.

“And when you watch it, I’m like, ‘What the hell?’ The camera was probably 45 miles away — it could have been a female stunt double, and you wouldn’t have known it was me running through glass!

“I had glass in my ears and hair for four days.”

Alan Ritchson said his manager told him, “You’re buying me an Aston Martin” in response to the show’s success.Brooke Palmer/Prime Video