List of The Big Bang Theory franchise characters

The American television sitcom franchise The Big Bang Theory, began with the multi-cam laugh track sitcom of the same name created and executive produced by Chuck Lorre and Bill Prady, which premiered on CBS on September 24, 2007, and ended on May 16, 2019, followed by the single-camera spinoff prequel television series Young Sheldon, created and executive produced by Lorre alongside Jim Parsons and Steven Molaro, which premiered on CBS on September 25, 2017, and concluded on May 16, 2024, with the third series in the franchise, a multi-cam spin-off sequel to Young Sheldon entitled Georgie & Mandy's First Marriage, premiering on October 17, 2024. A fourth series, a multi-cam spin-off sequel to The Big Bang Theory, will be entitled Stuart Fails to Save the Universe. It will feature Stuart Bloom, Denise, and Bert Kibbler, with Kevin Sussman, Lauren Lapkus, and Brian Posehn reprising their roles.

The Big Bang Theory initially centers on five characters: Sheldon Lee Cooper and Leonard Hofstadter, two physicists and roommates; Penny, their neighbor who is a waitress and aspiring actress; Sheldon and Leonard's friends and coworkers aerospace engineer Howard Joel Wolowitz and astrophysicist Raj Koothrappali.

Over time, several supporting characters have been introduced and promoted to starring roles, including physicist Leslie Winkle, neuroscientist Amy Farrah Fowler, microbiologist Bernadette Maryann Rostenkowski-Wolowitz, and comic book store proprietor and friend of the other characters Stuart Bloom. The series also features numerous supporting characters, each of whom plays a prominent role in a story arc. Included among them are parents of the main characters, their dates, and their coworkers. Celebrities such as Stephen Hawking appear in cameo roles as themselves.

Young Sheldon initially centers on Sheldon Cooper at the age of nine, going to high school and living with his family in the fictional town of Medford, East Texas, Sheldon's mother, Mary; his father and the head football coach at Medford High, George Sr.; his twin sister, Missy; his older brother, George Jr.; and his grandmother, Constance "Connie" Tucker, also known as "Meemaw". The series also features numerous supporting characters, each of whom plays a prominent role in a story arc. Included among them are Sheldon's present and former classmates, their dates and coworkers, and those of his family. Celebrities such as Elon Musk appear in cameo roles as themselves. Jim Parsons, who portrays the adult Sheldon Cooper on The Big Bang Theory, narrates the series and serves as an executive producer.

This section includes characters who have appeared in The Big Bang Theory, Young Sheldon, and Georgie & Mandy's First Marriage series with main role.

Leonard Leakey Hofstadter (portrayed by Johnny Galecki; seasons 1–12) is an experimental physicist with an IQ of 173. Originally from New Jersey, he received his PhD at age 24, spending at least some of his time at Princeton University. He shared an apartment in Pasadena with colleague and friend Dr. Sheldon Cooper for much of the series. Unlike his equally geeky friends, Leonard is interested and adept in building relationships with other people. Compared to his friends, he is relatively successful with women. Leonard comes from an accomplished family. His mother, Dr. Beverly Hofstadter, is a neuroscientist and world-renowned psychiatrist with whom he has a strained relationship. His sister is a medical researcher, his father, Dr. Alfred Hofstadter, is an anthropologist, and his brother Michael is a Harvard law professor. He and Penny date on and off throughout the series, eventually marrying and finding out that Penny is pregnant in the series finale.

Leonard makes a brief non-speaking cameo as a child in the Season 2 finale of Young Sheldon; he was portrayed by Isaac Harger as a child.

Sheldon Lee Cooper (portrayed by Jim Parsons; The Big Bang Theory seasons 1–12, Young Sheldon season 7; voiced by Parsons; narrator: Young Sheldon; and by Iain Armitage; guest: The Big Bang Theory season 12; main: Young Sheldon) is a theoretical physicist, possessing a B.S, M.S, M.A, Ph.D, Sc.D, I.Q. of 187, and eidetic memory. Born in East Texas, he was a child prodigy and received his PhD at age 16 from the California Institute of Technology. He is a cold, condescending, self-centered, and immature person but is rarely malicious. He is obsessed with routines and any disruptions distress him enormously. He shows signs of obsessive–compulsive personality disorder, often shown through his compulsive need to knock three times on a door while saying the name of the person behind the door three times too and the superiority complex. Despite his narcissism, selfishness, and lack of social graces, he does care about his friends and family. In seasons 1–9, he shares an apartment in Pasadena with friend and fellow physicist Dr. Leonard Hofstadter. From then after, he moves in with his girlfriend and eventual wife, Amy. It is revealed in Young Sheldon that they have kids too.