Born on Sept. 23, 1923, in Cairo to a wheat merchant who lived in the Nile Delta province of Qalyubia, Mohamed Hassanein Heikal —known in Egypt by his three-part name — turned away from the family business to seek a broader education at the American University in Cairo.

He is survived by his wife, Hedayet Olwi; three sons, Hassan Heikal, a former co-chief executive of the Cairo-based investment bank EFG Hermes; Ahmed Heikal, a founder of the Cairo-based private equity firm Citadel Capital; and Ali Heikal, a doctor; and seven grandchildren.

Mr. Heikal started his career in journalism at an English-language publication, The Egyptian Gazette, which sent him to cover the Battle of El Alamein. But he quickly moved to one of Cairo’s leading Arabic-language newspapers, and by the age of 24 he had won fame across the Arab world for his dispatches from the 1948 Arab war with Israel.

That is also when he first met Col. Gamal Abdel Nasser. “I have read your articles,” the colonel told him tersely, Mr. Heikal later recalled. “I expected to meet an older man.”

Their friendship began in 1951, when Nasser visited Mr. Heikal’s office to borrow a book he had written about Iran and tap his expertise. “The whole Egyptian underground was in contact with me,” Mr. Heikal later recalled.

But Mr. Heikal said he first realized an Egyptian coup was in the works only at the last moment, when he ran into Nasser at the home of an Egyptian Army general.

“The army failed in 1948 defending its honor. Now it does not even have its honor,” Mr. Heikal recalled saying, to which Nasser replied: “What do you suggest we do? Do you want the army to make a coup d’état?” Three days later, on July 22, 1952, Nasser did precisely that.