Mort Sahl, who confronted Eisenhower-era cultural complacency with acid stage monologues, delivering biting social commentary in the guise of a stand-up comedian and thus changing the nature of both stand-up comedy and social commentary, died on Tuesday at his home in Mill Valley, Calif., near San Francisco. He was 94.

The death was confirmed by Lucy Mercer, a friend helping oversee his affairs.

Gregarious and contentious — he was once described as “a very likable guy who makes ex-friends easily” — Mr. Sahl had a long, up-and-down career. He faded out of popularity in the mid-1960s, when he devoted his time to ridiculing the Warren Commission report on the assassination of President John F. Kennedy; then, over the following decades, he occasionally faded back in. But before that, he was a star and a cult hero of the intelligentsia.

He had regular club dates in New York, Chicago and San Francisco, with audiences full of celebrities. He recorded what the Library of Congress has cited as “the earliest example of modern stand-up comedy on record,” the album “At Sunset.” (Though recorded in 1955, it was not released until 1958, shortly after the release of his official first album, “The Future Lies Ahead.”) By 1960, he had starred in a Broadway revue, written jokes for Kennedy’s presidential campaign, hosted the Academy Awards, appeared on the cover of Time and been cast in two movies (he would later make a handful of others).

An inveterate contrarian and a wide-ranging skeptic, Mr. Sahl was a self-appointed warrior against hypocrisy who cast a jaundiced eye on social trends, gender relations and conventional wisdom of all sorts. Conformity infuriated him: In one early routine he declared that Brooks Brothers stores didn’t have mirrors; customers just stood in front of one another to see how they looked. Sanctimony infuriated him: “Liberals are people who do the right things for the wrong reasons so they can feel good for 10 minutes.”

But more than anything else, it was politicians who were the fuel for his anger. For that reason he was often compared to Will Rogers, whose death in 1935 had left the field of political humor essentially barren, though Mr. Sahl had none of Rogers’s homeyness and detested the comparison.

“I never met a man I didn’t like until I met Will Rogers,” he once said, despite never having met him. He described Rogers as a man who pretended to be “a yokel criticizing the intellectuals who ran the government,” whereas he himself pretended to be “an intellectual making fun of the yokels running the government.”

In December 1953, when Mr. Sahl first took the stage at the hungry i— the hip nightclub in San Francisco he helped make hip, where he would routinely be introduced as “the next president of the United States” — American comedy was largely defined by an unadventurous joke-book mentality. Bob Hope, Milton Berle and Henny Youngman may have been indisputably funny, but the rimshot gag was the prevailing form, the punch line was king, and mother-in-law insults were legion. It was humor for a smug and satisfied postwar society.

“Nobody saw Mort Sahl coming,” Gerald Nachman wrote in “Seriously Funny,” his book-length 2003 study of comedy in the 1950s and ’60s. “When he arrived, the revolution had not yet begun. Sahl was the revolution.”

Blazing a Trail

Mr. Sahl was a shock to the comedy system. Other groundbreaking comedians — Lenny Bruce, Dick Gregory, Woody Allen, Jonathan Winters, Joan Rivers, George Carlin and Richard Pryor among them — would pour into his wake, seizing on the awareness that audiences were hungry for challenge rather than palliation. And for social commentators who took to the airwaves in the half-century after he began to speak his mind — from Dick Cavett to Don Imus, Rush Limbaugh, Bill Maher and Jon Stewart — Mr. Sahl was their flag bearer as well.

(If a younger generation of comedians considered Mr. Sahl an inspiration, he did not return their love. He said in a 2010 interview that he found their comedy “kind of soft” and urged them to “take more chances.”)

“He just doesn’t bring to mind any other performer in the history of show business,” Mr. Cavett said after watching Mr. Sahl perform in 2004.

For one thing, he looked different from other comics of the time, eschewing the expected jacket and tie in favor of a more collegiate, informal look in an open-necked shirt and a V-neck sweater. And he peppered his routines with the language of youth and jazz — he was bugged, he dug this or that, he dated a lot of chicks. He took the stage carrying a rolled-up newspaper, a prop that was also a prompt; in Mr. Sahl’s performances, he talked about, anguished over and ranted at the news, spinning it with sardonic digressions, cryptic asides and blistering zingers.

“I’m for capital punishment,” he declared. “You’ve got to execute people — how else are they going to learn?”

In a vitriolic riff on Nikita Khrushchev’s 1959 visit to the United States — Mr. Sahl was virulently anti-Soviet — he spoke of an encounter between the Russian premier and Adlai Stevenson: “Khrushchev said to Stevenson, ‘If you want to be president, I want to tell you how to seize power,’ and Stevenson admonished him and said to him, ‘You know, that’s not the way we do things in this country,’ but several members of the Democratic advisory council who were present admonished Stevenson to keep quiet and listen to this man!”

Over the years he directed a venomous wit against Democrats and Republicans alike, famously supporting Kennedy in his presidential campaign against Richard M. Nixon and then lampooning him after his election: In choosing Kennedy, he said, the country was “searching for a son figure.”

His own political leanings were difficult to track. The left wanted to claim him, especially early in his career, but they couldn’t quite do so. Among other things, he could be crudely sexist and, though he supported civil rights, he was acerbic in confrontation with knee-jerk liberal dogma on the subject. Over the course of his life he kept company with politicians of varying stripes, from Stevenson, Kennedy and Eugene McCarthy to Alexander Haig and Ronald and Nancy Reagan. He said he had voted for Ross Perot; he praised Ron Paul and defended Sarah Palin; he cast a skeptical eye on Barack Obama’s presidency and was as scathing about Hillary Clinton as he was about Donald Trump.

“Are there any groups I haven’t offended?” he was wont to ask from the stage. He was best described, perhaps, as a pure iconoclast.

“If you were the only person left on the planet, I would have to attack you,” he once said. “That’s my job.”

The Barbs Begin

Morton Lyon Sahl was born in Montreal on May 11, 1927. His father, Harry, ran a tobacco shop, though he had grown up in New York as an aspiring playwright, and by the time Mort was 7, Harry Sahl had moved the family to Los Angeles and found work as a clerk for the Department of Justice. At 15, Mort joined the R.O.T.C. and left high school, lying about his age to join the Army; after two weeks, his mother, Dorothy, got him out.

After high school, he enlisted again and served in the Army Air Forces in Alaska, where his anti-authoritarian impulse first flowered. He edited a base newspaper called Poop From the Group, which needled military structure and routine and which earned him, he said, 83 straight days of mess-hall duty.

Following his discharge, he attended Compton Junior College and the University of Southern California, earning a degree in city management, and then followed a young woman — Sue Babior, whom he would eventually marry — to Berkeley. Prompted by Ms. Babior, he approached the owner of the hungry i, Enrico Banducci, for a performing gig, though it was mostly a music club. He got a tryout.

“I didn’t tell anyone, but I didn’t think he was so great,” Mr. Banducci recalled in “Seriously Funny.” He added: “I really looked at him and said, ‘Poor kid, he looks so skinny.’ I thought for 75 bucks a week he can’t hurt the place.”

Mr. Sahl’s early performances stayed away from politics. But within weeks he was commenting on the national scene, and that’s when his audience began to build.

He twitted Eisenhower for his dullness. Senator Joseph McCarthy became a favorite target: “Joe McCarthy doesn’t question what you say so much as your right to say it.” Lines from his act began appearing in newspaper columns, and when Herb Caen, the powerful San Francisco Chronicle columnist, gave Mr. Sahl’s act his imprimatur, his popularity took off.

He made record albums. He played college concerts. He appeared on television with Steve Allen and Jack Paar.

It was after Kennedy’s victory in the 1960 election that Mr. Sahl’s career first veered off track. He wrote barbed political one-liners for Kennedy the candidate, but when he turned his wit on the president-elect, tweaking him for his youth and for his family’s money and power, liberals who had loved his criticism of conservatism became notably cool.

On the occasion of Kennedy’s acceptance speech at the Los Angeles Coliseum, Mr. Sahl remarked slyly to a crowd estimated at 100,000 that Nixon had sent a congratulatory telegram to Joseph P. Kennedy, the president’s father: “You haven’t lost a son, you’ve gained a country.”

Whether Mr. Sahl was the victim of Kennedy family wrath or a blackball from liberal Hollywood, as he sometimes claimed, or whether his own thorniness was to blame — he bickered with producers and missed a number of engagements, and he was fired from a starring role in a 1964 Broadway play, Lorraine Hansberry’s “The Sign in Sidney Brustein’s Window” — gigs were fewer and farther between in the 1960s. In 1966, his attempt to open his own nightclub in Los Angeles failed when, he said, backers vanished after press previews.

“My so-called liberal supporters have all moved in with the establishment,” he said from the stage at one preview. “The same people who like jokes about John Foster Dulles and Goldwater suddenly freeze when they hear satirical humor about Vietnam or the war on poverty.”

Sahl the ‘Disturber’

He worked on radio and on local television in Los Angeles, but he didn’t help his cause with what some felt was an obsession with the Kennedy assassination. His performances began to include reading scornfully from the Warren Commission report. And he worked as an unpaid investigator for Jim Garrison, the New Orleans district attorney, who claimed to have uncovered secret evidence that Lee Harvey Oswald was not the assassin and who accused a New Orleans businessman, Clay Shaw, of conspiring to murder the president. No convincing evidence, secret or otherwise, was produced at Mr. Shaw’s trial, and the jury acquitted him in less than an hour.

“I spent years talking with people, Garrison notably, about the Kennedy assassination,” Mr. Sahl wrote in “Heartland,” a score-settling, dyspeptic memoir published in 1976, “and I was said to have hurt my career by being in bad company. I don’t thinkGene McCarthy is bad company. I don’t think that Jack Kennedy is bad company. I don’t think that Garrison is bad company.

“I learned something, though. The people that I went to Hollywood parties with are not my comrades. The men I was in the trenches with in New Orleans are my comrades.” He concluded, “I think Jack Kennedy cries from the grave for justice.”

No immediate family members survive. Mr. Sahl was married and divorced four times, first to Ms. Babior; then to China Lee, the first Asian American model to be a Playboy centerfold, from whom he was divorced for the second time in 1991; and finally to Kenslea Motter, from whom he was divorced in 2009. Mr. Sahl and his second wife had a son, Mort Jr., who died in 1996 of a drug overdose.

Though Mr. Sahl never reclaimed his central place in the entertainment firmament, he was somewhat resurgent in the 1970s, partly because Watergate reinvigorated the public appetite for derision aimed at politicians. He recorded an album, “Sing a Song of Watergate”; was booked by television hosts like Johnny Carson, Merv Griffin and David Frost; and continued to do college concerts.

“I’m not 18 anymore,” he lamented in “Heartland,” “but I’m the angriest man on any campus I visit.”

Indeed, Mr. Sahl never lost his fervor for pointing out life’s ironies and the hypocrisies of public figures. In 1987, in the wake of Jackie Mason’s successful one-man show, “The World According to Me!” he reappeared on Broadway in one of his own, “Mort Sahl on Broadway,” and he continued to perform in clubs long after that.

In recent years, feisty as ever despite deteriorating health, he had been performing one night a week in Mill Valley, where he had moved after four decades in Beverly Hills. His performances, at the Throckmorton Theater, were also streamed online and continued until the onset of the pandemic.

“I work as a disturber,” Mr. Sahl said in a Times interview after a 2004 performance, a reminder of lines from other decades and how little he’d changed.

Even at the height of his fame, in 1960, he was sardonic, bitterly ironic, unsparing.

“I’m the intellectual voice of the era,” he said to Time magazine, “which is a good measure of the era.”

Alex Traub contributed reporting.