She is a novel by H. Rider Haggard, first serialized in The Graphic from October 1886 to January 1887. In reprints it was extraordinarily popular in its day, and it has remained in print to the present {2006}.
It recounts the adventures of an expedition to an unexplored part of East Africa, where they find Ayesha, a beautiful and apparently immortal sorceress, who claims the expedition's leader as the reincarnation of her long-dead beloved. (Haggard gives a phonetic rendering of “Ayesha” as “assha”.) She had become ageless and perfectly beautiful more than 2 millennia earlier by immersing herself in a magic flame; she presses the expedition leader now to immerse himself as well.
This character was supposedly inspired by the Balobedu Rain Queen Masalanabo Modjadji.
The title is short for "She Who Must Be Obeyed", a translation of the Arabic honorific used for Ayesha by the Amahagger, a tribe whom she has enslaved. (The phrase acquired additional significance in British popular culture as the name by which John Mortimer's character Horace Rumpole refers to his wife.)