Born in Budapest, Hungary, in 1915, he was the son of a prominent restaurateur. With the onset of World War Two, he was conscripted into the Hungarian Army and served with the occupying forces after the Vienna Awards in Southern Slovakia and Northern Transylvania.

His father's business suffered during wartime, and was taken over by the Communists once Hungary fell under control of the Russians after the defeat of the Nazis.

Ronay emigrated to London, England alone on October 10, 1946. His father's contacts arranged for him to manage Princes restaurant in Piccadilly, and then the Carousel Club in St James's. He then borrowed £4,000 and took over the 39-seat Marquee, a former tea room near Harrods, putting classic French dishes on the menu, which was unusual for post-War UK.

The renowned TV chef Fanny Cradock visited with her husband, Johnny, and subsequently Ronay built up useful contacts with the press. After much cajoling, he began to write a food column for the Daily Telegraph.

In his later years, Ronay acted as food consultant for pub chain J D Wetherspoon, visiting outlets in his chauffeur driven car to ensure the onion rings were sufficiently crispy and the jacket potatoes up to standard. He also worked for motorway service station company Welcome Break, promoting their food and drinks.

In 1957, Ronay completed the first edition of the Egon Ronay's Guide to British Eateries, selling 30,000 copies. The guides gained in popularity and it became a mark of distinction to be mentioned in the books. Many restaurants proudly displayed blue roundels in their window saying "EGON RONAY'S GUIDES" for each year they were listed. The guides made a point of not accepting advertising or hospitality from hotels and restaurants to ensure their impartiality.

Ronay sold the rights to his books to the AA in 1985. However, after subsequent owner Leading Guides International went into bankruptcy, in 1997 Ronay went to court to claim back the guides which bore his name. In 2005, in conjunction with the Royal Automobile Club, Ronay brought out Egon Ronay's RAC Guide to the Top 200 Restaurants in the UK, basing the reviews on comments received by restaurant inspectors.

Twice married, his daughter Edina Ronay (b. 1944), is a former actress and fashion designer; his granddaughter, Shebah (b. 1972), is an actress and writer.

In various interviews, Ronay steadfastly refused to give his age. He died at his Berkshire home in Yattendon, on June 12, 2010, after a short illness.