Diamond Kingdom

Location: Unspecified; Outside of Japan
Episodes of Appearance: 022 - Romance Under the Moon! Usagi's First Kiss

The Diamond Kingdom is the name of a fictional kingdom which appears in both the anime and the manga. In the anime, it is mentioned in episode 022. Umino says that it is a very wealthy country that produces the most gemstones in the world. The kingdom has an embassy building in Tokyo, and a ball is held there in which the kingdom's first princess, Princess Dia, will present the kingdom's secret treasure to the world. Nephrite, Tuxedo Kamen, Luna, and the Sailor Senshi think that this treasure might be the Ginzuishou for which they have been searching, so they go to the ball to find out. The treasure does not turn out to be the Ginzuishou: in reality, it is a 2,000 carat diamond in the shape of Princess Dia.

The physical location of the kingdom is never mentioned in the anime or the manga, but in the manga, the location of the kingdom's embassy is stated to be at the bottom of Sendai Hill.