Publicist Susie Arons, a family representative, confirmed the death but did not give a specific cause.

“The Phil Donahue Show” (later just “Donahue”) debuted on a television station in Dayton, Ohio, on Nov. 6, 1967, with a single guest: atheist Madalyn Murray O’Hair, sometimes called the most hated woman in America for her effort to end Bible reading in schools. Other installments that first week included a video of a woman giving birth and a discussion on the appropriateness of dolls with penises.

On Mr. Donahue’s first day, the station had already invited a studio audience for the variety show that his program replaced, and he decided to let the crowd stay.

He chatted with audience members during commercial breaks and often liked what he heard. So one day, while on the air, “I jumped out of the chair and went into the audience,” he told NPR years later. “That moment is what … subsequently made the program different, and absorbing enough to hold a viewer for an hour.”

From that point on, Mr. Donahue, whose bright blue eyes and flying shirttails made him seem boyish — even after his dark hair turned prematurely white — was known for running up and down aisles with a microphone to seek comments from audience members, the vast majority of whom were women.

The humorist Erma Bombeck, a friend of his from Dayton, described Mr. Donahue as “every wife’s replacement for the husband who doesn’t talk to her.”

By 1979, the show was reaching 9 million viewers, nearly 8 million of them female. A Newsweek cover story from that time about Mr. Donahue described him as possessing “an intuitive ability to place himself in his audience’s head and ask the questions they would ask.” But he could be intrusive. Newsweek reported that when “a trio of female impersonators” talked about their work, Mr. Donahue “broke in with: ‘Let me ask you this — where do you guys go to the bathroom?’ The audience applauded.”

Over the years, he interviewed late night host Johnny Carson, pop star Elton John, boxer Muhammad Ali, anti-apartheid leader Nelson Mandela, comic filmmaker Mel Brooks, and tennis rivals Billie Jean King and Bobby Riggs. Some of his more controversial guests included Albert Speer, Adolf Hitler’s architect; novelist Ayn Rand; Nation of Islam leader Louis Farrakhan; Ku Klux Klan grand wizard David Duke; and adult-film star Harry Reems.

In 1987 he taped five episodes of “Donahue” in the Soviet Union, using a satellite hookup to connect viewers in the rival superpowers. He was among the first TV hosts to address the issue of sexual abuse by priests. (A self-described “lapsed Catholic,” Mr. Donahue once told Knight Ridder Newspapers that “organized religion has been very unfair to God.”)

Writing in the Los Angeles Times in 1990, author Dennis McDougal praised Mr. Donahue for his “razor-sharp, no-nonsense probing of Watergate figures, foreign dignitaries and Love Canal environmental malefactors during the 1970s.” Mike Douglas, the host of a frothier daytime talk show, told Newsweek: “He works like a crack attorney in front of the jury box.” Donahue won a Peabody Award in 1980 for his “ability to ask the tough questions without seeming to offend” and his “innate sense of honesty.”

He also earned a shelf’s worth of Emmy Awards, and in May he visited the White House to receive the Presidential Medal of Freedom.

Mr. Donahue never claimed to be impartial. He was an ardent liberal — his most frequent guest was Ralph Nader, whose presidential campaign he later supported. He belonged to the National Organization for Women, attributing what he described as his sexism early in life to his religious education.

“We were so busy trying to avoid sin that we could never make friends with women, never share ideas, never care how they felt,” he told TV Guide in 1978.

Mr. Donahue moved his show to Chicago in 1974, and, 11 years later, he relocated once again, to New York, to be near his second wife, actress Marlo Thomas. For years, Mr. Donahue was a regular contributor to NBC’s “Today Show” and was talked about as a possible anchor. But his talk show lost viewers as he began to face imitators including Winfrey, Geraldo Rivera and Sally Jessy Raphael.

To improve his ratings, Mr. Donahue experimented with stunts and increasingly prurient or titillating subject matter. He recorded one episode featuring a “cross-dresser fashion show” while wearing a skirt and another that explored the Australian tavern pastime of shot-putting people with dwarfism.

Of the second, he said he was simply reporting on a phenomenon. “I didn’t toss the dwarfs,” he told the Los Angeles Times defensively.

He did draw crowds with topics like breast enlargement and guests like disgraced televangelist Tammy Faye Bakker and flamboyant socialite and actress Zsa Zsa Gabor. Journalist and historian David Halberstam, a longtime admirer, told the L.A. Times in 1990 that “Donahue” had “lost its soul.”

Ratings continued to slide and, in 1995, New York’s WNBC dropped the show, depriving Mr. Donahue of an outlet in the media capital. His final episode aired on Sept. 13, 1996.

Winfrey paid tribute: “Phil really opened the door to this genre, and for that, I am grateful. I have said from the very first day of my show, if there hadn’t been a Phil, there wouldn’t have been a me.” At the time of his retirement, he had completed nearly 7,000 programs.

‘Norman Rockwell’ childhood

Phillip John Donahue was born in Cleveland on Dec. 21, 1935. His mother was a homemaker, and his father sold furniture. “I had a Norman Rockwell type childhood,” he said in a videotaped interview with the Television Academy Foundation.

He attended Catholic schools, serving as an altar boy, before enrolling at the University of Notre Dame, where he worked as an entry-level assistant at a university-owned radio station. After receiving a business and marketing degree in 1957, he was hired by KYW radio in Cleveland, where he filled in for an announcer who was on vacation.

In 1958 he took a radio job in Adrian, Mich., that included covering local news. “It was a baptism. I fell in love with the whole idea of journalism,” he said in the Television Academy Foundation interview. “I thought it was the noblest calling.”

The following year he moved to Dayton’s WHIO to anchor the morning newscast; he later added an afternoon call-in show. But he was bored. “I had gone as far as I was going to go” at WHIO, he wrote in his 1979 autobiography, “Donahue: My Own Story.” “My enthusiasm was dying as my job became routine.”

In 1967 he left broadcasting and briefly took a job as a salesman with a trading stamp company before returning to host a morning television talk show on WLWD (now WDTN), also in Dayton. Mr. Donahue said he never thought the show would become so popular.

But Carson, Lucille Ball, Gloria Steinem, Jane Fonda and other newsmakers found their way to the Dayton studio. In 1970, the show entered national syndication. By the end of the 1970s, it was seen in almost 200 cities, reaching more households, according to Broadcasting magazine, than any other syndicated talk show.

Mr. Donahue and his first wife, Margaret Cooney, divorced in 1975. After the breakup, Mr. Donahue’s four sons lived with him in Chicago, while his daughter moved to Albuquerque with Cooney. His job meant he couldn’t spend as much time with his sons as he would have liked.

“I have this dream that I’m enchanting the world while my kids are at home smoking grass,” he said during a panel discussion in Washington on raising children. His solution? “I go on a week’s trip and take two of them along. It halves my worry.”

In 1977 he met Thomas when she appeared on his program to promote “Free to Be You and Me,” a children’s book and album about sexism. “It was embarrassing. We flirted outrageously for a full hour,” Thomas told Joan Rivers in 1984.

Mr. Donahue called her the next day. The two began what The Washington Post called “an old-fashioned drugstore romance, circa 1948. A two-straw affair with lots of starry-eyed gazing, hand-holding, stolen glances, secret smiles.” The couple married in 1980. They lived in Manhattan and Westport, Conn.

In addition to his wife, survivors include four children from his first marriage, Mary Rose, Kevin, Michael and Danny Donahue; a sister; and two grandchildren. Another son from his first marriage, James, died in 2014.

In 2002, Mr. Donahue came out of retirement to host a show on MSNBC, in direct competition with conservative host Bill O’Reilly’s program on Fox News. Mr. Donahue, an opponent of the war in Iraq and holder of other antiestablishment views, was ready to take the gloves off. As he told Winfrey in an interview for her magazine, “I’m not 29 anymore, my wife isn’t pregnant, I’m not trying to raise kids, I don’t have a mortgage — so it takes less courage for me to speak up.”

But the network canceled the show the next year, blaming low ratings. A leaked memo later revealed that some executives considered Mr. Donahue a “difficult public face for NBC in a time of war.” He said he was ordered to bring on two conservative guests for every liberal.

Mr. Donahue and Thomas published a book in 2020, “What Makes a Marriage Last,” including 40 interviews with celebrities and others on what challenges they have faced in their marriages through the years. In 2021 they launched a podcast, “Double Date,” based on the same premise.

Looking back on his three decades on the air, Mr. Donahue reached back to his boyhood, and a less than illustrious Little League Baseball career, to explain what made talk shows his forte.

“I talked a lot when I was a child,” he told People magazine in 1996. “I was small, and I was always good enough to make the team, but I never distinguished myself. I’d get my two hits of the season, so I was always on the brink of greatness — in my own childhood mind — but I never excelled. I think to make up for that, I probably just talked.”