Lenny Bruce was born Leonard Alfred Schneider in Mineola, New York, grew up in nearby Bellmore and attended Wellington C. Mepham High School. His youth was chaotic; his parents divorced when he was five years old and Lenny moved in with various relatives over the next decade. His mother, Sally Marr (née Sadie Kitchenberg), was a stage performer who had an enormous influence on Bruce's career. After spending time working on a farm with a family that provided the stable surroundings he needed, Bruce joined the United States Navy at the age of 17 in 1942, and saw active duty in Europe. In May 1945 he reported to his ship's medical officer that he was experiencing homosexual urges. This led to his Undesirable Discharge in July 1945. However, he had not admitted to or been found guilty of any breach of naval regulations and successfully applied to have his discharge changed to one "Under Honorable Conditions ... by reason of unsuitability for the naval service".

After a short stint in California spent living with his father, Bruce settled in New York City looking to make it as a comedian. However, he was in possession of little to differentiate himself from the thousands of other showbiz hopefuls that populated the city. One locale where these hopefuls congregated was Hanson's, the diner where he first met the comedian Joe Ancis, who had a profound influence upon Bruce's approach to comedy. What Bruce did in his acts later on was a direct reflection of his meticulous schooling by Ancis.

In 1947, soon after changing his last name to Bruce, he earned $12 and a free spaghetti dinner for his first stand-up performance in Brooklyn, New York. He later was a guest ... introduced by his mother, who called herself "Sally Bruce" ... on the Arthur Godfrey's Talent Scouts show, doing a "Bavarian mimic" of American movie stars (e.g., Humphrey Bogart).

Bruce met his future wife, Honey Harlow, a stripper from Baltimore, Maryland, in 1951. They were married that same year, and Bruce was determined to get her off the stage. This desire resulted in Bruce pursuing schemes designed to make as much money as possible, the most notable of which was the Brother Mathias Foundation scam, which resulted in Bruce being arrested in Miami, Florida later that year for impersonating a priest. He had been soliciting donations for a leper colony in British Guiana (now Guyana) under the auspices of the "Brother Mathias Foundation", which he had legally chartered - the name was his own invention, but possibly referred to the actual Brother Matthias who had befriended Babe Ruth at the orphanage to which Ruth had been confined as a child. Bruce had stolen several priests' clergy shirts and a clerical collar while posing as a laundry man. He was found not guilty because of the legality of the New York state-chartered foundation, the actual existence of the Guiana leper colony, and the inability of the local clergy to expose him as an impostor. Later, in his semifictional autobiography How to Talk Dirty and Influence People, Bruce revealed that he had made about $8,000 in three weeks, sending $2,500 to the leper colony and keeping the rest.

In 1953, Bruce and Harlow eventually left New York for the West Coast, where they got work as a double act at the Cup and Saucer in Los Angeles, California. Bruce then went on to join the bill at the club Strip City. Harlow found employment at the Colony Club, which was widely known to be the best burlesque club in Los Angeles at the time.

In late 1954, Bruce left Strip City and found work within the San Fernando Valley at a variety of strip clubs. As the master of ceremonies, his job was to introduce the strippers while performing his own ever-evolving material. The clubs of the Valley provided the perfect environment for Bruce to create new routines: according to Bruce's primary biographer, Albert Goldman, it was "precisely at the moment when he sank to the bottom of the barrel and started working the places that were the lowest of the low" that he suddenly broke free of "all the restraints and inhibitions and disabilities that formerly had kept him just mediocre and began to blow with a spontaneous freedom and resourcefulness that resembled the style and inspiration of his new friends and admirers, the jazz musicians of the modernist school."

Bruce's early comedy career included writing the screenplays for Dance Hall Racket in 1953, which featured himself, his wife, Honey Harlow, and mother, Sally Marr, in roles; Dream Follies in 1954, a low-budget burlesque romp; and a children's film, The Rocket Man, in 1954. He also released four albums of original material on Berkeley-based Fantasy Records, with rants, comic routines, and satirical interviews on the themes that made him famous: jazz, moral philosophy, politics, patriotism, religion, law, race, abortion, drugs, the Ku Klux Klan, and Jewishness. These albums were later compiled and re-released as The Lenny Bruce Originals. Two later records were produced and sold by Bruce himself, including a 10-inch album of the 1961 San Francisco performances that started his legal troubles. Starting in the late 1950s, other unissued Bruce material was released by Alan Douglas, Frank Zappa and Phil Spector, as well as Fantasy. Bruce developed the complexity and tone of his material in Enrico Banducci's North Beach nightclub, "The hungry i," where Mort Sahl had earlier made a name for himself.

His growing fame led to appearances on the nationally televised Steve Allen Show, where he made his debut with an unscripted comment on the recent marriage of Elizabeth Taylor to Eddie Fisher, wondering, "will Elizabeth Taylor become bar mitzvahed?" He also began receiving mainstream press, both favorable and derogatory. Syndicated Broadway columnist Hy Gardner called Bruce a "fad" and "a one-time-around freak attraction", while Variety declared him "undisciplined and unfunny".On February 3, 1961, in the midst of a severe blizzard, he gave a famous performance at Carnegie Hall in New York. It was recorded and later released as a three-disc set, titled The Carnegie Hall Concert. In the liner notes, Albert Goldman described it as follows:

On October 4, 1961, Bruce was arrested for obscenity at the Jazz Workshop in San Francisco; he had used the word "cocksucker" and riffed that "'to' is a preposition, 'come' is a verb", that the sexual context of "come" is so common that it bears no weight, and that if someone hearing it becomes upset, he "probably can't come". Although the jury acquitted him, other law enforcement agencies began monitoring his appearances, resulting in frequent arrests under charges of obscenity. The increased scrutiny also led to an arrest in Philadelphia, for drug possession the same year, and again in Los Angeles, California, two years later. The Los Angeles arrest took place in then-unincorporated West Hollywood, and the arresting officer was a young deputy named Sherman Block, who would later become County Sheriff. The specification this time was that the comedian had used the word "schmuck", an insulting Yiddish term that is also an obscene term for penis.

In April 1964, he appeared twice at the Cafe Au Go Go in Greenwich Village, with undercover police detectives in the audience. On both occasions, he was arrested after leaving the stage, the complaints again pertaining to his use of various obscenities.

A three-judge panel presided over his widely publicized six-month trial, with Bruce and club owner Howard Solomon both found guilty of obscenity on November 4, 1964. The conviction was announced despite positive testimony and petitions of support from Woody Allen, Bob Dylan, Jules Feiffer, Allen Ginsberg, Norman Mailer, William Styron, and James Baldwin — among other artists, writers and educators, and from Manhattan journalist and television personality Dorothy Kilgallen and sociologist Herbert Gans. Bruce was sentenced, on December 21, 1964, to four months in the workhouse; he was set free on bail during the appeals process and died before the appeal was decided. Solomon later saw his conviction overturned; Bruce, who died before the decision, never had his conviction stricken.

Despite his prominence as a comedian, Bruce appeared on network television only six times in his life. In his later club performances Bruce was known for relating the details of his encounters with the police directly in his comedy routine; his criticism encouraged the police to subject him to maximum scrutiny. These performances often included rants about his court battles over obscenity charges, tirades against fascism and complaints that he was being denied his right to freedom of speech.

He was banned outright from several U.S. cities, and in 1962 was banned from performing in Sydney, Australia. At his first show there Bruce took the stage, declared "What a fucking wonderful audience" and was promptly arrested.

Increasing drug use also affected his health. By 1966 he had been blacklisted by nearly every nightclub in the United States, as owners feared prosecution for obscenity. Bruce did have a famous performance at the Berkeley Community Theatre in December 1965. It was recorded and became his last (live) album, titled "The Berkeley Concert"; his performance here has been described as lucid, clear and calm, and one of his best. His last performance took place on June 25, 1966, at The Fillmore Auditorium in San Francisco, on a bill with Frank Zappa and The Mothers of Invention. The performance was not remembered fondly by Bill Graham, who described Bruce as "whacked out on amphetamines"; Graham thought that Bruce finished his set emotionally disturbed. Zappa asked Bruce to sign his draft card, but the suspicious Bruce refused.

At the request of Hugh Hefner and with the aid of Paul Krassner, Bruce wrote an autobiography. Serialized in Playboy in 1964 and 1965, this material was later published as the book How to Talk Dirty and Influence People. Hefner had long assisted Bruce's career, featuring him in the television debut of Playboy's Penthouse in October 1959.

On August 3, 1966, Bruce was found dead in the bathroom of his Hollywood Hills home at 8825 N. Hollywood Blvd. The official photo, taken at the scene, showed Bruce lying naked on the floor, a syringe and burned bottle cap nearby, along with various other narcotics paraphernalia. Record producer Phil Spector, a friend of Bruce's, bought the negatives from the photographs to keep them from the press. The official cause of death was "acute morphine poisoning caused by an accidental overdose."

He was interred in Eden Memorial Park Cemetery in Mission Hills, California, but an unconventional memorial on August 21 was controversial enough to keep his name in the spotlight. The service saw over 500 people pay their respects, led by Spector. Cemetery officials had tried to block the ceremony after advertisements for the event encouraged attendees to bring box lunches and noisemakers. Dick Schaap eulogized Bruce in Playboy, with the memorable last line: "One last four-letter word for Lenny: Dead. At forty. That's obscene."

Bruce is survived by his daughter, Kitty Bruce, who lives in Pennsylvania.

At the time of his death his girlfriend was comedienne Lotus Weinstock.

On December 23, 2003, 37 years after his death, Bruce was granted a posthumous pardon for his obscenity conviction by New York Governor George Pataki.