KRYSTEN RITTER is quick to mention that she never fancied herself a superhero actor. She’s not even, she believes, what you expect a comic-book heroine to look like.

But a casting director whom Ritter knew asked her to try out for Marvel’s new Netflix series, “Jessica Jones” (debuts Friday), and the 33-year-old actress — so known for roles in “Breaking Bad” and “Don’t Trust the B in Apartment 23″ — soon found herself cast as the title character on a comics-inspired show, playing a street-level antihero.

Once Ritter learned she was the next “Defender” of Hells Kitchen, she embarked on what she called an enjoyable reading binge about all things Jessica Jones.

“I started doing some research [with the comics] and was so pleasantly surprised by every step of the process, learning more about the character,” Ritter told The Post’s Comic Riffs. “How complex she was. How dark the material was. The fact that it is also Marvel and a part of this global super-brand and huge, expanding Marvel Cinematic Universe. It just kept getting better with each piece of information I was given.”

Being a part of Marvel’s interconnected cinematic universe that extends to their television works is great, Ritter said. But the actress  is most enthused by the Netflix formula that allows “Jessica Jones” to approach the darkest and grittiest of material, which would otherwise have no place in Marvel’s live-action offerings.

“That’s been the fun part for me. Being a part of the Marvel world — but being a part of them doing something so different [with Netflix] that it is a total departure from the movies from Marvel as we know it — is so exciting,” Ritter said. “You have this giant support behind you, but this is such a dark, character-driven … really an actor’s piece.

“It’s a role that sometimes you only find in dark, tiny little [independent films], in terms of the complexity and the amount of [character] development,” she said. “So honestly, I feel like I kind of won the lottery.”

Ritter’s Jones is a retired superhero who has beyond-above-average strength, though not the best flying ability (think of it as an extended jump). And she might have had the superhero life of her Avengers peers, but that is not where viewers will meet her. Instead, we find Jones in the darkest shadows of Hells Kitchen, trying to piece her life together after coming across a villain (David Tennant’s Kilgrave, who will be “Jessica Jones” main bad guy) who makes her realize that a brightly costumed, PG-13 superhero life will sometimes only help you discover how dark and R-rated things can really be.

“She’s rebuilding her life as a private investigator in New York City,” Ritter said. “She’s very rough around the edges. She doesn’t involve herself in any social communities. She keeps her world very small. She’s not interested in saving the universe or the city. She just wants to lay low and drink whiskey.”

Jessica Jones’s isolated life as a failed superhero brings with it a surprisingly understanding companion when she comes across Mike Colter’s Luke Cage.

Colter’s Cage, like Ritter’s Jones, is a character who has “special abilities” that he’d rather just keep to himself. Jones and Cage begin a complicated relationship that, Ritter said, she’s glad made it to the production board. While studying all things Jessica Jones, she said, the relationship with Luke Cage was one of her favorite aspects of the story.

“You really can’t talk about [Jessica Jones] without touching upon her relationship with Luke Cage,” Ritter said. “They are, in a way, total opposites, but then at their core, they’re very similar and kind of the same person. They are shying away from the outside world. They’re very internal, very introverted people, but they have this thing. They have this special thing that sets them apart and they really connect on this deep, chemical level.

“I loved in the comic books, more than anything, the relationship with Luke Cage,” she continued. “It’s a relationship we haven’t really seen before.”

Ritter said that any apparent on-screen chemistry when viewers first meet Jones and Cage can be attributed to her and Colter being a part of “Jessica Jones” from the very beginning — starting with having to audition on the same day.

“I feel like, personally, we started this whole process together,” Ritter told Comic Riffs. “We were screen-testing together. This whole thing started with us together. It’s rare as an actor that you can bond with somebody in that way, because you’re usually on a journey all on your own.

“But we’re doing this show together, he’s doing ‘Luke Cage’ and we’ll be doing ‘The Defenders’ together as well,” the Pennsylvania-sprung actress continued. “So it’s really nice to have somebody to be on the ride with you.

“He and I are pretty close. He’s a great actor. He’s a great team partner, not too bad to look at and yeah … ,” she continued. “We got lucky. It doesn’t always work that way that you can have such great chemistry with your scene partner.”

As for Tennant’s Kilgrave, on the other hand, Ritter said that the two didn’t film much together when production on “Jessica Jones” started, but once they were together, she found herself watching in awe.

“That guy [Tennant] can take a five-page scene and do it over and over a million different ways each time and still hit every line,” Ritter said. “Working with him because of the character dynamic, I got to kind of watch him and enjoy that. When the camera was on him, I was really just like checking out what he was doing as an actor, and I was completely blown away by it.”

As for her near-future team-up: Her Jessica Jones will join forces with Charlie Cox’s Daredevil, Colter’s Luke Cage and the stiil-to-be-cast Iron Fist — a show that will join all of Marvel’s Netflix properties to form a gritty Avengers team known as “The Defenders.” Ritter said that the antihero get-together is part of what made signing on for “Jessica Jones” such a fun choice.

“I’m totally excited” about “The Defenders,” she said. “I think that the casting has been really exciting. I love who they’re getting for all of these shows.

“They told me from the beginning they were going to get the best actors, the best writers, the best directors, and they really have. I’m thrilled to be a part of the bigger picture. It’s a huge opportunity for me as an actress to land this role because it’s on Netflix and [being a part of] two shows.

“This is a really rare thing that I certainly don’t take lightly.”