Tenjou Utena is the heroine of the Japanese comic and anime Revolutionary Girl Utena. The original comic did not posses the same darkness that the anime would come to have, but both forms of the narrative established Utena, as well as many other members of the cast, as icons of adolescent alternative sexuality. It is often included in the "yuri" genre- a loose canon tied together by the theme of female love.
It's one giant, complex allegory, and Utena is a girl who wants to be a prince and save princesses. In her story, she is given a princess to protect almost immediately. We are led through the light and darkness of adolescence through symbol and reference, helped along by swordfights and so, so many roses.
For anime fans interested in possibly-lesbian-narratives growing up in the nineties, Utena was the 102 course to Yuri 101: Sailor Uranus and Sailor Neptune. Utena was not a unique character is theme– the heroine-who-dresses-up-as-a-prince trope is preceded by Lady Oscar and Princess Sapphire– but she was accessible to that generation as the comic and anime were licensed and translated in the United States at that time.
The story of Revolutionary Girl Utena unfolds much like a play, three acts establishing allegories of virtues, sins, and the apocalypse. It was disguised at first as a shoujo (girls) story, but gradually revealed itself to be rather dark and twisted- it was artful, and led to the production of a movie so bizarre fans are not sure whether to mention that particular incarnation to anyone.