Tuxedo Mask (タキシード仮面, Takishīdo Kamen?) is a fictional character and the primary male protagonist of the Sailor Moon metaseries. His real name is Mamoru Chiba (地場 衛, Chiba Mamoru?, Darien in the English versions), but he disguises himself in order to support the series' central heroines, the Sailor Senshi. Wearing a mask to conceal his identity, he interferes with enemy operations, offers the Senshi advice, and sometimes physically aids them in battle.

Although he is not a Senshi, Tuxedo Mask possesses a power item like theirs, a Sailor Crystal, which gives him guardianship over the planet Earth. He also has psychic powers, including psychometry and healing, which evolve and are important to the story in the manga, but which are minor and remain static in the anime. He is the primary love interest for Sailor Moon and a significant player in much of the story, having been royalty in the "past life" storyline as well as in the future.

He is referred to in the Japanese version as "Tuxedo Kamen" while the dub refers to him as "Tuxedo Mask" when calling this character by his codename. He is also commonly known by the nickname used by Chibiusa and Usagi, "Mamo-chan." The dub often shortened his name, "Darien" to "Dar" as a nickname, however this was often inconsistent.

Source: Wikipedia