Walter Hartwell White Sr., also known by his clandestine alias Heisenberg, is a fictional character and the main protagonist of Breaking Bad. He is portrayed by Bryan Cranston. A chemistry honours graduate of the California Institute of Technology, Walt co-founded the company Gray Matter Technologies with his close friend Elliott Schwartz and his then-girlfriend Gretchen. He left Gray Matter abruptly, selling his shares for $5,000; soon afterwards, the company made a fortune, much of it from his research. Walt subsequently moved to Albuquerque, New Mexico, where he became a high school chemistry teacher. Breaking Bad begins on Walt's 50th birthday, when he is diagnosed with Stage IIIA lung cancer. After this discovery, he resorts to manufacturing methamphetamine and drug dealing with his former student Jesse Pinkman (Aaron Paul) to ensure his family's financial security after his death. He is pulled deeper into the illicit drug trade, becoming more and more ruthless as the series progresses, and later adopts the alias "Heisenberg", which becomes recognizable as the kingpin figure in the local drug trade. Series creator Vince Gilligan has described his goal with Walter White as "turning Mr. Chips into Scarface" and deliberately made the character less sympathetic over the course of the series. Walt's evolution from the mild-mannered school teacher and family man to ruthless criminal mastermind and murderer is the show's central focus.
Although AMC officials initially hesitated to cast Cranston due to his previous comedic role on Malcolm in the Middle, Gilligan cast him based on the actor's past performance in the X-Files episode "Drive", which Gilligan wrote. Cranston contributed greatly to the creation of his character, including Walt's backstory, physical appearance, and personality traits.
Both the character and Cranston's performance have received critical acclaim, with White frequently being mentioned as one of the greatest and most iconic television characters of all time. Cranston won four Primetime Emmy Awards for Outstanding Lead Actor in a Drama Series, three of them being consecutive, becoming the second actor to do so, after Bill Cosby for I Spy in the 1960s. Following his fourth win, Cranston tied Dennis Franz for the most wins in the category's history. He is the first man to win a Critics' Choice, Golden Globe, Primetime Emmy, and Screen Actors Guild Award for his performance.