The Shitennou (四天王, Shitennō?, Four Heavenly Kings) are a group of villains from the Sailor Moon metaseries. They are sub-leaders of the very first villain group, the Dark Kingdom, working directly under Queen Beryl, and provide the major antagonistic force for the beginning of every version of the series—manga, anime, musicals, and live-action.
The group's title, shitennou, comes from Buddhist mythology. They are frequently referred to among fans as the "Generals," a term which never appears in the series, but which references their position in the Dark Kingdom. Each member has epaulettes on his uniform, which can be used to deduce their respective ranks.
In the manga, the Shitennou originally functioned as the four guardians of Earth's crown prince, Endymion. They were led astray during the time of the Silver Millennium, finally selling their souls to the Dark Kingdom and becoming Queen Beryl's servants. When reincarnated in the 20th century, they again fall prey to her and obey her every command, but retain a sense that they need to seek out their real master and aid him. In the manga, they continue to appear after the first season as spirit-advisors to Mamoru, the reincarnation of Endymion. This backstory was not included in the anime, but was reintroduced and built upon for the stage musicals and even more so live-action series.
In DiC's English adaptation of the anime, the Shitennou were human-like beings from the Negaverse, an alternate dimension of evil, and had only a vague understanding of human ways. From dialogue between Nephlite (Nephrite) and Zoycite (Zoisite), they were even required to take classes in human psychology to blend in.