George Carlin on Red Pills and Blue Pills

George Denis Patrick Carlin was born at New York Hospital in Manhattan on May 12, 1937, the second of two sons born to Mary (née Bearey, 1896–1984) and Patrick John Carlin (1888–1945). Carlin had an older brother, Patrick Jr. (1931–2022), who later had a major influence on his comedy. His mother was born in New York City to Irish immigrants and his father was himself an Irish immigrant from Cloghan, a village in County Donegal in Ulster, leading Carlin to later describe himself as "fully Irish". He wrote in his posthumously published autobiography Last Words that, when his first wife Brenda was alive, "I used to have a fantasy of Ireland, the southeastern parts so that it would be a little warmer, and the two of us there, close enough to Dublin that you could go buy things you needed." His parents separated when he was two months old because of his father's alcoholism, so his mother raised him and his brother on her own. His father died when Carlin was eight years old. Carlin's maternal grandfather, Dennis Bearey, was an NYPD police officer, who wrote out the works of William Shakespeare by hand for fun.

Carlin said that he picked up an appreciation for the effective use of the English language from his mother, though they had a difficult relationship and he often ran away from home. He grew up on West 121st Street in the Morningside Heights neighborhood of Manhattan, which he and his friends called "White Harlem" because it "sounded a lot tougher than its real name". He attended Corpus Christi School, a Roman Catholic parish school of the Corpus Christi Church in Morningside Heights. One of Carlin's best childhood friends was fellow student Randy Jurgensen who went on to become one of the most decorated homicide detectives in the NYPD's history. His mother owned a television, which was a new technology few people owned at the time, and Carlin became an avid fan of the pioneering late-night talk show Broadway Open House during its short run. He went to the Bronx for high school but, after three semesters, was expelled from Cardinal Hayes High School at age 15. He briefly attended Bishop Dubois High School in Harlem and Salesian High School in Goshen. He spent many summers at Camp Notre Dame in Spofford, New Hampshire, where he regularly won the camp's drama award. Later, at his request, some of his ashes were spread at Spofford Lake upon his death.

Carlin joined the U.S. Air Force and trained as a radar technician. He was stationed at Barksdale Air Force Base in Bossier City, Louisiana, and began working as a disc jockey at radio station KJOE in nearby Shreveport. Labeled an "unproductive airman" by his superiors, he received a general discharge on July 29, 1957. During his time in the Air Force, he had been court-martialed three times and received many nonjudicial punishments and reprimands.

In August 1960, while touring with comedy partner Jack Burns in Dayton, Ohio, Carlin met Brenda Hosbrook. They were married at her parents' home in Dayton on June 3, 1961. The couple's only child, Kelly Marie Carlin, was born on June 15, 1963. The two renewed their wedding vows in Las Vegas in 1971. Hosbrook died of liver cancer on May 11, 1997, the day before Carlin's 60th birthday. Six months later, he met comedy writer Sally Wade, and later described it as "love at first sight" but admitted that he was hesitant to act on his feelings so soon after his wife's death. He eventually married Wade in a private and unregistered ceremony on June 24, 1998. The marriage lasted until Carlin's death in 2008, two days before their 10-year anniversary.

In a 2008 interview, Carlin stated that using cannabis, LSD, and mescaline had helped him cope with events in his personal life. He also stated several times that he had battled addictions to alcohol, Vicodin, and cocaine, and spent some time in a rehab facility in late 2004. Although born into a Catholic family, he vocally rejected religion in all of its forms, and frequently criticized and mocked it in his comedy routines. When asked if he believed in God, he responded, "No. No, there's no God, but there might be some sort of an organizing intelligence, and I think to understand it is way beyond our ability.

Carlin had a history of heart problems spanning three decades. This included heart attacks in 1978, 1982, and 1991; an arrhythmia requiring an ablation procedure in 2003; a significant episode of heart failure in 2005; and two angioplasties on undisclosed dates. On June 22, 2008, at the age of 71, he died of heart failure at Saint John's Health Center in Santa Monica, California. His death occurred one week after his last performance at The Orleans Hotel and Casino. In accordance with his wishes, his body was cremated and his ashes were scattered in front of various New York City nightclubs and over Spofford Lake in New Hampshire, where he had attended summer camp as an adolescent.