The past life and alter ego of Tsukino Usagi who lived in the Moon Kingdom during the age of the Silver Millennium. Her royal guardians and closest friends (also princesses) were Sailor Mercury, Sailor Mars, Sailor Jupiter, and Sailor Venus.
Usagi occasionally took the form of Princess Serenity during climactic moments, when more strength was needed. Serenity amplifies her power using the Maboroshi no Ginzuishou.
By appearance, Princess Serenity is seen in a white flowing gown and openly shows the crescent moon on her forehead. In the manga her hair is long and white, while in the anime it is blond.