Sailor Moon (セーラームーン Sērā Mūn) is a fictional character in the Sailor Moon metaseries and the main protagonist of the franchise, as well as its title character. Her civilian name, Usagi Tsukino (月野 うさぎ Tsukino Usagi), becomes Serena Tsukino in the English-language versions. A carefree schoolgirl, she can transform herself into the de facto leader of the series' primary heroines, the Sailor Senshi.
Due to the series' widespread popularity in many countries and to her distinctive and oft-copied odango hairstyle, she has become one of the most immediately recognizable and iconic anime characters worldwide. No other character appears in all 200 episodes of the anime, and Usagi is present in all 52 acts of the manga as well as all 51 acts of the live-action series.
Serena, Usagi's given name in the English-language versions of the series, derives from "Serenity", the name Usagi went by in her past life. In the English manga she is mostly called by the nickname Bunny, which is the literal meaning of usagi. Her boyfriend for most of the series, Mamoru Chiba, calls her by the affectionate nickname "Usako" (a diminutive, the suffix -ko meaning "child").