The Big Bang Theory is reportedly ending because of Jim Parsons

"The Locomotion Reverberation"-- Pictured: Sheldon Cooper (Jim Parsons). Leonard and Wolowitz try to distract Sheldon when he slows the progress of their guidance system. Also, Penny and Amy take Bernadette out for the night, leaving Raj and Stuart to care for baby Halley, on THE BIG BANG THEORY, Thursday, Feb. 9 (8:00-8:31 PM, ET/PT), on the CBS Television Network. Dean Norris returns as Colonel Williams.

The Big Bang Theory will end next year because Jim Parsons wanted to leave the show, according to reports.

CBS was attempting to negotiate with the stars of its hit sitcom, which is set to end after 12 seasons of science-based humour, to sign on for another two years – but Parsons refused.

The star, who married his long-term partner Todd Spiewak last year, was set to make more than $50 million from the new deal, according to Entertainment Weekly.

The show is set to end soon after it passes the 300-episode mark (CBS)

But Parsons, who is already the highest-paid gay actor in the world, decided to walk away instead, leading showrunners to end the series after 300 episodes instead of struggling on without his character, Sheldon Cooper.

Earlier this year, the 45-year-old actor spoke out in support of genderfluid people ahead of the release of his film, A Kid Like Jake.

The film – which also stars Claire Danes, Priyanka Chopra and Octavia Spencer – focuses on New York couple Greg and Alex Wheeler and their four-year-old son, who exhibits gender non-conforming behaviour.

Jim Parsons and Todd Spiewak got married last year (Dimitrios Kambouris/Getty)

Parsons said he “felt very strongly” about the issue, and that he had every hope that the next generation would make strides towards full equality.

He pointed to the response to the deadly Parkland shooting in February as evidence, saying: “I was watching back in March, after the Florida school shooting, and it was just so moving to see a younger generation taking to the streets, on their feet, and speaking so eloquently and passionately.

“As a 45-year-old gay man, who’s been able to be an out and working actor, I feel grateful for the time I grew up in, but I feel like there’s a level of inclusiveness and openness to all sorts of human beings that we’ve never seen as a society before,” he continued.

Parsons has won four Primetime Emmy Awards and a Golden Globe for his portrayal of Sheldon Cooper (MARK RALSTON/AFP/Getty)

“Even in our best of times, we’ve never quite known it to the level we might know it in the next 15 or 20 years, as this generation comes into prominence and power.

“You get that impression that you’re dealing with a whole generation that has grown up thinking it’s not okay to slander people for being gay and more recently, slander people for gender fluidity,” Parsons added.

“It’s a different world and it sounds like, quite possibly, a better world.”

Priyanka Chopra, Silas Howard, Claire Danes, Leo James, Jim Parsons and Amy Landecker attend the 'A Kid Like Jake' Premiere during the 2018 Sundance Film Festival at Eccles Center Theatre on January 23, 2018 in Park City, Utah. / AFP PHOTO / ANGELA WEISS (Photo credit should read ANGELA WEISS/AFP/Getty Images)

Parsons with the other stars of A Kid Like Jake (ANGELA WEISS/AFP/Getty)

The actor, who came out in 2012 after a New York Times writer outed him, said that the film “takes a little bit of mystery and a little bit of fear away from a topic that could feel very lonely.

“The movie doesn’t offer any answers or solutions, but what it does is make it okay to ask dumb questions, to fumble with something that you don’t fully understand.”