was a French writer. She has written numerous books, including J'ai quinze ans et je ne veux pas mourir (1955) ('I am Fifteen and I Do Not Want to Die'). Arnothy eventually married Claude Bellanger (1909–1978). Arnothy was born in Budapest, Hungary.
J'ai quinze ans et je ne veux pas mourir is based on her diary, which recorded her experience as a teenager during the 1945 siege of Budapest. Arnothy fled Hungary with her parents. When she arrived in France, her diary was the only possession she still had. The book was reviewed in Harper's Magazine in 1956. It received good reviews also from The Daily Express, The New York Times, Herald Tribune, San Francisco Examiner, Kirkus, L.A. Herald Express, Chicago Sunday Tribune and The Times. She later published a sequel, It Is Not So Easy to Live, a second part which does not come from her journal but from her memory; she chronicles her escape via Vienna to Paris, where she eventually settled and married.
She also wrote a couple of detective stories under the pseudonym William Dickinson and many other books. No one work has been so successful as J'ai quinze ans et je ne veux pas mourir, which has been considered by some authors (i.e.: Sándor Márai as a masterpiece of the literature about the Second World War.