Elena Poniatowska was born in Paris to Prince Jean Evremont Poniatowski Sperry and Paula Amor-Escandón. Her father was a Polish nobleman who was a descendant of the brother of King Stanislaus II of Poland, the last king of Poland. The Poniatowski brothers of King Stanislaus were granted Princely titles as relatives to the King. She also is descendant of King Louis XV of France through her paternal great-grandmother Louis Le Hon. Her mother, Paulette Amor e Iturbe, was a Mexican of mixed French ancestry, and also a descendant of Mexican nobility.
Poniatowska fled from France with her mother during the Second World War. The family settled in Mexico City, where the young Elena and her sister Kitzia learned Spanish from an Indian servant. In 1943, Elena was sent to study to the United States. She returned to Mexico in 1953 and started her career as a journalist working for the newspaper Excélsior.
She is best known for her 1971 work La noche de Tlatelolco (published in English as Massacre in Mexico), in which she relates her interviews with survivors and families of those who died in the 1968 Tlatelolco massacre in Mexico City. Since then she has published several works of fiction, testimonial literature, as well as book compilations of her interviews with writers, artists, and politicians. In recent years her prominence as a public intellectual and political figure in Mexico has increased.
Since 2005, Poniatowska has been an active supporter of Andrés Manuel López Obrador. In April 2006 she appeared in a series of television commercials denouncing the attempts of the other two major parties, particularly the National Action Party, to link López Obrador to leftist President Hugo Chávez of Venezuela.
Her aunt was Mexican aristocrat Guadalupe ´Pita´Amor. Her sister lives abroad.