Ganondorf is the final boss of most games in the Zelda series. In the games Ganondorf is the leader of a race of desert brigands called the 'Gerudo' and the evil archenemy of Link. His specific motives vary from game to game but most often they include him kidnapping Princess Zelda and planning to achieve domination of Hyrule and presumably the world beyond it. To this end he seeks the Triforce, a magical relic giving the holder ultimate power. Currently he already possesses a portion of the Triforce called the Triforce of Power which gives him great strength but not enough to accomplish his ends leading him to hunt the remaining Triforce pieces. Unlike Link and Zelda he is the same character in every game with the exception of Four swords adventures where he is a reincarnation. He is also the physical personification of the demon King Demise's hatred and is destined to reincarnate eternally if he is actually killed.

Source: Wikipedia, "Characters in The Legend of Zelda series," available under the CC-BY-SA License.