Studio One was a long-run American dramatic radio-television anthology series, created in 1947 by the 26-year-old Canadian director Fletcher Markle, who came to CBS from the CBC.

Markle launched the 60-minute radio series on CBS April 29, 1947, with an adaptation of Malcolm Lowry's Under the Volcano. Broadcast on Tuesdays, opposite Fibber McGee and Molly and The Bob Hope Show, the radio series continued until July 27, 1948, showcasing such adaptations as Dodsworth, Pride and Prejudice, The Red Badge of Courage and Ah, Wilderness. Then Markle and the show made a quantum leap to television.

Sponsored by Westinghouse Electric Corporation, the television series was seen on CBS (which Westinghouse acquired in 1995) from 1948 through 1958, under several variant titles: Studio One Summer Theatre, Studio One in Hollywood, Summer Theatre, Westinghouse Studio One and Westinghouse Summer Theatre.

Offering a wide range of dramas, Studio One received Emmy nominations every year from 1950 to 1958. The series staged some notable and memorable teleplays among its 466 episodes. Some created such an impact they were adapted into theatrical films. Reginald Rose's acclaimed drama 12 Angry Men, about the conflicts of jurors deciding a murder case, originated on Studio One on September 20, 1954, and the 1957 motion picture remake with Henry Fonda was nominated for three Academy Awards. Sal Mineo had the title role in Reginald Rose's Dino (January 2, 1956), and he reprised the role for the movie Dino (1957).

For years, the original TV production of 12 Angry Men was considered lost. However, in 2003, Joseph Consentino, a researcher-producer for The History Channel, discovered a kinescope of the Studio One production in the home of the late New York defense attorney (and later judge) Samuel Leibowitz. Consentino was researching a History Channel documentary about Leibowitz, and the discovery was announced by the Museum of Televsion & Radio (now The Paley Center for Media). This was detailed by Cynthia Littleton in the Hollywood Reporter: In 1954, Crime at Blossoms, scripted by Jerome Ross, was given an Edgar Award for Best Episode in a TV Series. Nathaniel Hawthorne's granddaughter received a plaque in recognition of her grandfather's writing achievements, during the April 3, 1950 telecast of The Scarlet Letter.

The Night America Trembled was Studio One's September 9, 1957 top-rated television recreation of Orson Welles' radio broadcast of The War of the Worlds on October 30, 1938. The cast included Alexander Scourby, Ed Asner and Warren Oates. James Coburn made his television debut, and John Astin appeared uncredited as a reporter. In one of his earliest acting roles, Warren Beatty appeared in the bit part of a card-playing college student.

Worthington Miner, Martin Manulis and others produced. As spokeswoman for Westinghouse, Betty Furness became strongly identified with Westinghouse products, and she also was seen in eight Studio One dramas. The show's musical directors were Milton C. Anderson (who also created music for Playhouse 90) and Eugene Cines.

A third season episode of the ABC legal drama Boston Legal, "Son of the Defender," used clips from the Studio One episode "The Defender," featuring William Shatner as an attorney joining his lawyer father (Ralph Bellamy) in the defense of a 19-year-old accused of murder. Utilizing clips of the older show for flashbacks, the Boston Legal episode portrayed Shatner's Studio One character as a young Denny Crane trying his first case alongside his father.

In 2007, the November 14, 1954 broadcast of "I'm a Fool" starring James Dean and Natalie Wood was shown at the annual Mid-Atlantic Nostalgia Convention in Aberdeen, Maryland. Many episodes of Studio One are available for viewing at The Paley Center for Media in New York City and Los Angeles.

Originally a CBS radio dramatic anthology series, which was directed by Fletcher Markle who was often heard on the series in leading roles with his future wife, Mercedes McCambridge.

For many years, only the first half of the kinescope of the live 1954 TV version of "12 Angry Men" (shown as an episode of this series, and upon which the movie version (12 Angry Men (1957)) is based) was thought to survive, and had been in the possession of the Museum of Television & Radio since 1976. In 2003 a complete 16mm kinescope was discovered in the collection of Samuel Liebowitz (former defense attorney and judge) and was also acquired by the museum.