Dejah Thoris is a Red Martian Princess from the city of Helium. She is the granddaughter of Tardos Mors, Jeddak of Helium.
Dejah Thoris is the love interest and later the wife of John Carter, an Earthman mystically transported to Mars who rescued her from the Green Martians, and subsequently the mother of their son Carthoris and daughter Tara.
In Allan and the Sundered Veil, while trapped in the chrono-crystal aleph, a 'time lost' Carter sees a vision of himself fighting a Green Martian and winning Dejah Thoris, who is here described as "almost naked ruby-clad princess." At the start of Volume II, when John Carter and Gullivar Jones discuss the planned attack on the Mollusc, Gullivar tells John he is sorry for what happened to "The princess". This suggests Dejah Thoris was captured or killed by the mollusk invaders, but it is also theorized that V2 takes place in the year long interval she was held captive in the Temple of the Sun following the events of The Gods of Mars.
Dejah Thoris was created by Edgar Rice Burroughs and appears as a prominent character in several novels of the Barsoom series.
Her appearances in LoEG media are limited to verbal references, and she is never refferred by any name, as the character is not in the public domain in the European Union.