A fascinating article at Wikipedia: “List of premature obituaries.” A smattering of the dozens of entries:

ABBA: Members of the pop group were declared dead by a German Newspaper in 1976. It was claimed they had been killed in an aeroplane crash, with only member Anni-Frid Lyngstad surviving, but badly disfigured.[3] The group appeared on German television to disprove the rumour.

Pope Benedict XV, whose pneumonia in January 1922 caused worldwide expectation of his impending death. His death was prematurely announced by a New York newspaper with the front-page headline “Pope Benedict XV is dead”, followed by a later edition headlined “Pope has remarkable recovery.” However, the Pope did subsequently die of the illness on 22 January.

Lal Bihari, Indian founder of the Association of the Dead, an organisation which highlights the plight of people in Uttar Pradesh who are incorrectly declared dead by relatives in order to steal their land, usually in collusion with corrupt officials. Bihari himself was officially dead from 1976 to 1994 as a result of his uncle’s attempt to acquire his land. Among various attempts to publicize his situation and demonstrate that he was alive, he stood for election against Rajiv Gandhi in 1989 (and lost). He was awarded the Ig Nobel Peace Prize in 2003 for his ‘posthumous’ activities.

Nicephorus Glycas: in 1896, having presumably been declared dead, the Greek Orthodox bishop of Lesbos awoke in his coffin after he had been lying in state for two days. He sat up and asked what mourners were staring at.

Ernest Hemingway: after the author and his wife Mary Welsh Hemingway were involved in two African plane crashes in 1954, newspapers reported that both had died. Hemingway survived, but suffered extensive injuries which affected him for the rest of his life. AE Hotchner claimed that Hemingway read a scrap book of his obituaries every morning with a glass of champagne after the incident.[80] Hemingway committed suicide in 1961.[81]