Dragon Quest (ドラゴンクエスト, Doragon Kuesuto?), published as Dragon Warrior in North America until the 2005 release of Dragon Quest VIII: Journey of the Cursed King, is a series of role-playing games created by Yuuji Horii and published by Square Enix (formerly Enix). Installments of the series have appeared on MSX computers, Famicom/NES, Super Famicom/Super NES, Game Boy Color, Game Boy Advance, Nintendo DS, PlayStation, PlayStation 2 and Wii video game consoles, as well as on several models of mobile phone. As of December 19, 2007, the Dragon Quest series has sold over 43 million units worldwide. It is Square Enix's second most successful franchise and is arguably the most popular video game franchise in Japan.

Dragon Quest's North American name was changed due to a trademark conflict with the role-playing game DragonQuest, which was published by veteran wargame publisher SPI in the 1980s until the company's bankruptcy in 1982 and purchase by TSR, which then published it as an alternate line to Dungeons & Dragons until 1987. In 2003, Square Enix registered the Dragon Quest trademark in the US, making the Dragon Warrior name obsolete.

Source: Wikipedia