McGoohan was born in Astoria, Queens, New York City, to Thomas McGoohan and Rose Fitzpatrick, who were living in the United States after emigrating from Ireland to look for work. He was raised Roman Catholic. Shortly after he was born, McGoohan's parents moved back to Mullaghmore, County Sligo, Ireland, and, seven years later, they moved to Sheffield, England. McGoohan attended St Vincent's school in Sheffield, but following the outbreak of World War II he was evacuated to Loughborough, Leicestershire. There he attended Ratcliffe College, where he excelled in mathematics and boxing.
McGoohan left school aged sixteen and returned to Sheffield where he worked as a chicken farmer, a bank clerk and a lorry driver before getting a job as a stage manager at Sheffield Repertory Theatre. When one of the actors became ill McGoohan filled in, launching his acting career.
In 1955, McGoohan starred in a West End production of a play called Serious Charge in the role of a priest accused of being gay. Orson Welles was so impressed by McGoohan's stage presence ("intimidated," Welles said later) that he cast him as Starbuck in his York theatre production of Moby Dick Rehearsed.
While working as a stand-in during actress screen tests, McGoohan was signed to a contract with the Rank Organisation, the largest European production company between 1930 and 1960. The producers may have been more interested in capitalizing on his boxing skill and appearance than his acting ability, casting him as the conniving bad boy in such films as the gritty Hell Drivers and the steamy potboiler The Gypsy and the Gentleman, and after a few films and some clashes with the management, the contract was dissolved.
Soon, producer Lew Grade approached him about a TV series in which he would play a spy named John Drake. Having learned from his experience at the Rank Organisation, McGoohan insisted on several conditions in his contract before agreeing to appear in the program: all the fistfights should be different, the character would always use his brain before using a gun, and, much to the horror of the executives, no kissing.
The series debuted in 1960 as Danger Man, a half-hour program geared toward an American audience. It did fairly well, but not as well as hoped in the US. Production lasted only one year and 39 episodes. It was resurrected in 1964, broadcast in the United States as Secret Agent (a one-hour program) and completed two broadcast seasons. It was rerun in several countries and gained cult status worldwide. After the series was over one interviewer asked McGoohan if he would have liked the series to continue, to which he replied, "I would rather do twenty TV series than go through what I went through under that Rank contract I signed a few years ago for which I blame no one but myself."
McGoohan spent some time working for Disney on The Three Lives of Thomasina and The Scarecrow of Romney Marsh. He had already turned down the roles of James Bond and Simon Templar (The Saint) when Lew Grade asked him if he would like to give John Drake another try. This time, McGoohan had even more say about the series; it was expanded to an hour and the writing was changed to allow McGoohan more acting range. The popularity of the series exploded. McGoohan became the highest paid actor in the UK and the show lasted almost three more series.
After shooting the first two episodes of Danger Man in colour going into its third season, McGoohan told Lew Grade he was going to quit for another show. 
In the face of McGoohan's intention to quit Danger Man Grade asked if he would at least work on "something" for him. McGoohan gave him a run-down of what would later be called a miniseries about a secret agent who resigns suddenly and wakes up to find himself in a prison disguised as a holiday resort. Grade asked for a budget, McGoohan had one ready, and they made a deal over a handshake early on a Saturday morning to produce The Prisoner.
McGoohan not only produced, but also wrote, directed and starred in the show. He used two pseudonyms, writing "Free for All" as Paddy Fitz and directing "Many Happy Returns" and "A Change of Mind" as Joseph Serf. He also wrote "Once Upon A Time" and "Fall Out" using his own name. The seven episodes were increased to seventeen.
The Prisoner spends the entire series trying to escape from The Village and to learn the identity of his nemesis, Number One. The Prisoner was a completely new, cerebral kind of series, stretching the limits of the established television formulas. Its influence has been echoed in Lost, Babylon 5, Nowhere Man, I-man, Tower Prep,The Truman Show, The Simpsons and ReBoot.
The main character, the unnamed Number Six, became McGoohan's most recognisable character. Unfortunately, it also became his prison. Number Six was so obsessively pro-individual that whenever McGoohan later played someone who had something to say about individuality or freedom, the character was often compared to his previous incarnation; for example, his portrayal of the warden in Escape from Alcatraz. "Mel Gibson will always be Mad Max, and me, I will always be a Number," he was once quoted as saying.
The cult of The Prisoner spawned many books, college courses, a quarterly magazine and documentaries. There were several fan clubs - most notably "Six of One", which honours the show annually with a convention in Portmeirion, Wales, where the show's exteriors were shot. McGoohan was the honorary president. In the May 30, 2004 edition of TV Guide, The Prisoner was ranked seventh in a list of the "25 Top Rated Cult Shows Ever!" McGoohan's show outranked the likes of The Twilight Zone (#8) and Doctor Who (#18). TV Guide wrote, "Fans still puzzle over this weird, enigmatic drama, a Kafkaesque allegory about the individual's struggle in the modern age."
McGoohan appeared in many films, including Howard Hughes's favourite, the 1968 film Ice Station Zebra, for which he was critically acclaimed, and Silver Streak (1976), with Gene Wilder and Richard Pryor. In 1977, he starred in the TV series Rafferty playing a former army doctor who has retired and moved into private practice (one reviewer considers this series a forerunner to House, M.D.). He also appeared in the 1981 film Scanners, a science fiction/horror film by Canadian director David Cronenberg that has since attained cult movie status.
McGoohan received two Emmy Awards for his work on Columbo with his long-time friend Peter Falk. Patrick McGoohan had said that his first appearance on Columbo was probably his favorite American role. He directed five Columbo episodes (including three of the four in which he played the murderer), and wrote and produced two (including one of these). McGoohan was involved with the Columbo series, in one way or another, from 1974 to 2000.
In 1991, he starred in Masterpiece Theatre's production of The Best of Friends for PBS, which told the story of the unlikely friendship between a museum curator, a nun and a playwright. McGoohan played George Bernard Shaw alongside Sir John Gielgud as Sydney Cockerell and Dame Wendy Hiller as Sister Laurentia McLachlan.
He was most recognized by a later generation of fans as the Machiavellian King Edward "Longshanks" from the 1995 Oscar-winning Braveheart. In 1996, he appeared as Judge Omar Noose in A Time to Kill. He directed Richie Havens in a rock-opera version of Othello called Catch My Soul.
In 2000, he reprised his role as Number Six in an episode of The Simpsons, "The Computer Wore Menace Shoes". In it, Homer Simpson concocts a news story to make his website more popular, and he wakes up in a prison disguised as a holiday resort. Dubbed Number Five, he befriends Number Six and escapes with his boat.
McGoohan's name was linked to several aborted attempts at producing a new motion picture version of The Prisoner. In 2002, director Simon West (Lara Croft: Tomb Raider) was signed to helm a version of the story. McGoohan was listed as executive producer for the film, which never came to fruition. More recently, director Christopher Nolan attached to a proposed film version. However, the source material remained difficult and elusive to adapt into a feature film. Ultimately, a reimagining of the series was filmed for the AMC network in late 2008, with broadcast taking place in November 2009; McGoohan was not involved in the project.
McGoohan was one of several actors considered for the role of James Bond in Dr. No (along with future Bond actor Roger Moore). Part of McGoohan's popular legend is that he turned down the role on moral grounds (the same grounds that would affect how he played John Drake). The success of the Bond films is generally cited as the reason for Danger Man being revived in 1964, which led in turn to The Prisoner. McGoohan, a Catholic, introduced himself as “Drake. John Drake” in the style of James Bond for the series “Secret Agent.” But that’s where the comparison ended. While the Bond character was — and remains — quite the womanizer, McGoohan said his faith made him resist having his Drake character fall into the same lifestyle as Bond.
Despite his extensive British stage experience, he appeared on Broadway only once. In 1985, he starred opposite Rosemary Harris in Hugh Whitemore's Pack of Lies, in which he played a British intelligence agent. He was nominated for a Drama Desk Award as Best Actor for his performance.
A biography of the actor was published in 2007 by Tomahawk Press.
McGoohan fell in love with an actress named Joan Drummond, to whom he reportedly wrote love notes every day. They were married on May 19, 1951. They had three daughters, Catherine (born 1952), Anne (born 1959) and Frances (born 1960). The McGoohans settled in the Pacific Palisades district of Los Angeles in the mid-1970s.