After he made his mark in London in the 1970s, he went on to play a wide range of roles, including Edward VII, Oscar Wilde and Winston Churchill.Michael Gambon, the Irish-born actor who drew acclaim from both audiences and peers for his stage and screen work, and who won even wider renown as Albus Dumbledore, the firm but kindly headmaster of the Hogwarts wizarding school, in the “Harry Potter” films, died on Wednesday night. He was 82.Mr. Gambon’s family confirmed his death in a brief statement issued on Thursday through a public relations company. “Michael died peacefully in hospital with his wife, Anne, and son Fergus at his bedside, following a bout of pneumonia,” the statement said. It did not identify the hospital where he died.The breakthrough that led the actor Ralph Richardson to call him “the great Gambon” came with Mr. Gambon’s performance in Bertolt Brecht’s “Life of Galileo” at London’s National Theater in 1980, although he had already enjoyed modest success, notably in plays by Alan Ayckbourn and Harold Pinter.Peter Hall, then the National Theater’s artistic director, described Mr. Gambon (pronounced GAM-bonn) as “unsentimental, dangerous and immensely powerful.” He recalled in his autobiography that he had approached four leading directors to accept him in the title role, only for them to reject him as “not starry enough.”After John Dexter agreed to direct him in what Mr. Gambon was to describe as the most difficult part he had ever played, the mix of volcanic energy and tenderness, sensuality and intelligence he brought to the role — in which he aged from 40 to 75 — excited not only critics but also his fellow performers.Mr. Gambon in the title role of Bertolt Brecht’s “Life of Galileo” at the National Theater in London in 1980. He called it the most difficult part he had ever played.Donald Cooper/AlamyAs Mr. Hall recalled, the dressing-room windows at the National, which look out onto a courtyard, “after the first night contained actors in various states of undress leaning out and applauding him — a unique tribute.”That brought Mr. Gambon a best-actor nomination at the Olivier Awards. He would win the award in 1987 for his performance as Eddie Carbone in Arthur Miller’s “A View From the Bridge” at the National Theater. Again it was his blend of vulnerability and visceral force that impressed audiences; Miller declared that Mr. Gambon’s performance as the embattled longshoreman was the best he had seen. Mr. Ayckbourn, who directed the production, described Mr. Gambon as awe-inspiring.“One day he just stood in the rehearsal room and just burst into tears — no turning upstage, no hands in front of his face,” Mr. Ayckbourn said. “He just stood there and wept like a child. It was heartbreaking. And he did angry very well too. That could be scary.”Michael John Gambon was born in Dublin on Oct. 19, 1940. He became a dual British and Irish citizen after he and his seamstress mother, Mary, moved to London to join his father, Edward, an engineer helping to reconstruct the city after it had been badly bombed in 1945.By his own admission he was a dreamy student, often lost in fantasies of being other people, and he left school “pig ignorant, with no qualifications, nothing.” When the family moved from North London to Kent, he became an apprentice toolmaker at Vickers-Armstrongs, which was famous for having built Britain’s Spitfire fighter planes.The teenage Mr. Gambon had never seen a play — he said he didn’t even knew what a play was — but when he helped build sets for an amateur dramatic society in Erith, Kent, he was given a few small roles onstage. “I went vroom!,” he recalled. “I thought, Jesus, this is for me, I want to be an actor.” He joined the left-leaning Unity Theater in London, performing and taking lessons in improvisation at the Royal Court.This emboldened him to write to Micheal MacLiammoir and Hilton Edwards, the founders of the Gate Theater in Dublin, claiming to be a West End actor passing through the city en route to New York. An invitation ensued, as did a job as the Second Gentleman in “Othello,” followed by an offer to join Laurence Olivier’s new National Theater, which (Mr. Gambon said) was seeking burly six-footers like himself to play spear carriers.Several small or nonspeaking roles followed — Mr. Gambon remembered little but saying “Madam, your carriage awaits” to Maggie Smith in a Restoration comedy — until Olivier himself advised him to seek better parts in the provinces. That he did, closely modeling an Othello in Birmingham in 1968 on the Moor famously played at the National by Olivier, an actor Mr. Gambon said he always regarded with “absolute awe.”Mr. Gambon didn’t make his mark in London until 1974, when he played a slow-witted veterinary surgeon in Alan Ayckbourn’s trilogy “The Norman Conquests.” One scene, in which he sat on a child’s chair so low that only half his face was visible, became celebrated for the hilarity it generated. Indeed, Mr. Gambon said, he actually witnessed a man “laugh so much he fell out of his seat and rolled down the gangway.”Mr. Gambon in 1987, the year he won an Olivier Award for his performance in Arthur Miller’s “A View From the Bridge.”John Stoddart/Popperfoto, via Getty ImagesMr. Gambon said he disliked looking in mirrors; so unpleasant did he find his face that he compared it to a crumpled plastic bag. His jowls and his heavy build meant that he never played Hamlet or any obviously heroic or conventionally good-looking characters, yet he won universal admiration for his versatility. He seemed able to grow or shrink at will. For a man compared to a lumberjack, he was astonishingly fleet and nimble. One critic saw him as a rhinoceros that could almost tap-dance.And he brought a paradoxical delicacy to many a role: King Lear and Antony, which he played in tandem for the Royal Shakespeare Company; leading roles in Pinter’s “Betrayal” and “Old Times”; Ben Jonson’s Volpone at the National Theater; and the anguished restaurateur in David Hare’s “Skylight,” a performance he took from London to Broadway, where it earned him a Tony Award nomination for best actor in 1996.At the time he was best known in the United States for a television performance as the daydreaming invalid in Dennis Potter’s acclaimed 1986 mini-series, “The Singing Detective.” Though he always said that the theater was his great love and he pined for it when he was away, he often appeared on screens both large and small during a career in which he was virtually never out of work.Before being cast as Dumbledore, Mr. Gambon was best known in the United States for his performance as the daydreaming invalid in Dennis Potter’s acclaimed 1986 mini-series, “The Singing Detective.”BBCFrom 1999 to 2001, he won successive best-actor BAFTA awards, for “Wives and Daughters,” “Longitude” and “Perfect Strangers.” His portrayal of Lyndon B. Johnson in the 2002 mini-series “Path to War” won him an Emmy nomination, as did his Mr. Woodhouse in the 2009 adaptation of Jane Austen’s “Emma.”His television roles varied from Inspector Maigret to Edward VII, Oscar Wilde to Winston Churchill. And in film he played characters as different as Albert Spica, the coarse and violent gangster in Peter Greenaway’s “The Cook, the Thief, His Wife & Her Lover,” and the benign Professor Dumbledore.Mr. Gambon took over the role of Dumbledore, a central character in the Harry Potter saga, when Richard Harris, who had originated it, died in 2002. Reviewing “Harry Potter and the Prisoner of Azkaban,” in which he first appeared in the role, A.O. Scott of The New York Times wrote that the film, though noteworthy for its special effects, was also, like the two earlier films in the series, “anchored by top-of-the-line flesh-and-blood British acting,” and noted that “Michael Gambon, as the wise headmaster Albus Dumbledore, has gracefully stepped into Richard Harris’s conical hat and flowing robes.” Mr. Gambon continued to play Dumbledore through the final movie in the series, “Harry Potter and the Deathly Hallows: Part 2,” released in 2011.For all the attention that role brought him, Mr. Gambon claimed not to see this or any other performance as a great accomplishment; he tended to answer interviewers who questioned him about acting by saying, “I just do it.” But in fact he prepared for his roles conscientiously. He would absorb a script, then use rehearsals to adapt and deepen his discoveries.“I’m very physical,” he once said. “I want to know how the person looks, what his hair is like, the way he walks, the way he stands and sits, how he sounds, his rhythms, how he dresses, his shoes. The way your feet feel on the stage is important.” And slowly, very slowly, Mr. Gambon would edge toward what he felt was the core of a person and, he said, rely on intuition to bring him to life onstage.Though he was no Method actor, Mr. Gambon did use memories when strong emotions were needed. He found it easy to cry onstage, he said, sometimes by thinking of the famous photograph of a naked Vietnamese girl running from a napalm attack. Acting, he said, was a compulsion, “a hard slog, heartache, misery — for moments of sheer joy.”Mr. Gambon in the 1989 film “The Cook, the Thief, His Wife & Her Lover.”Steve Pyke/Getty ImagesIn person Mr. Gambon was elusive; he said that he didn’t exist aside from his acting and that he hated the idea of celebrity, even popularity. He adamantly refused to reveal anything about his private life to interviewers, though it’s on public record that he married Anne Miller when he was 22 and that together they had a son, Fergus. They both survive him. It is believed that they remained on good terms even after he had two other sons, Tom and William, with the set designer Philippa Hart.He was knighted in 1998.His engineering apprenticeship left him fascinated with the workings of mechanical things: clocks, old watches and especially antique guns, of which he possessed scores. He also took delight in fast cars; he once appeared on the television show “Top Gear” and drove so recklessly that a section of the track he’d taken on two wheels was renamed Gambon Corner.He became notorious for impish behavior on and off the stage. A qualified pilot, he promised to cure a fellow actor of his fear of flying by taking him up in a tiny plane, then mimed a heart attack as, his tongue lolling, he nose-dived toward outer London. Mr. Ayckbourn recalled a moment in “Othello” when Mr. Gambon shoved Iago’s head into a fountain. “Shampoo and set, shampoo and set,” roared the Moor — but such was the emotion already generated the audience reportedly didn’t notice.“I’m actually serious about my work,” Mr. Gambon once said. However, much of that work came to a premature end after he played a wily, drunken, needy Falstaff at the National Theater in 2005, followed by the alcoholic Hirst in Pinter’s “No Man’s Land” in 2008.Having admitted that he often felt terrified before making an entrance, he had panic attacks while rehearsing the role of W.H. Auden in Alan Bennett’s “The Habit of Art” in 2009 and was twice rushed to a hospital before withdrawing from the production. By then he was finding it difficult to remember lines. After playing the nonspeaking title character in Samuel Beckett’s “Eh Joe” in 2013, he announced that he would no longer perform onstage.He continued to appear on film and television, notably as the ailing title character in “Churchill’s Secret” in 2016. But his departure from theater meant that he ended his stage career with a deep sense of loss.“It’s a horrible thing to admit,” he said. “But I can’t do it. And it breaks my heart.”Alex Marshall More