Roronoa Zoro, nicknamed Pirate Hunter Zoro (Kaizoku-Gari no Zoro), is a skilled swordsman who uses up to three swords at once, clutching the third in his mouth. To fulfill a promise he made to a childhood friend named Kuina, he wants to become the world's greatest swordsman by defeating Mihawk(the one of the seven warlords of the sea).
Before joining Luffy, he made a living by bounty hunting. He joins Luffy's crew in exchange for his aid in escaping execution. He makes it clear that he would turn on his captain if he ever stepped between him and his dream, but unknown to Luffy, Zoro thinks that if he cannot protect Luffy's dream, his own would have no meaning and is even willing to die for it. His physical strength is enough to lift a building. During a fight with Baroque Works agent Daz Bones(or Mr. 1), he learns how to cut through solid steel which can hear breathe from the steel and cut through the part with the less breathe sound. He can employ an "Asura" technique which gives him three faces and six arms, thus totaling nine swords. In addition, Zoro can expand the muscle mass of his arms. He is extremely poor at understanding geographical directions and gets lost very easily. He also sleeps a great deal and loves to drink.Zoro ranked second in all three Shōnen Jump character popularity polls. Furthermore, in a 2007 poll by Oricon, Zoro was voted as the 4th most desired character to receive a spinoff. Talk praises Zoro's "hilarious" three-sword fighting style as a great example of the show's sense of humor. Holly Ellingwood from Activeanime praised Zoro's fight against Luffy as one of the best moments from the 10th DVD from the series released by Viz Media, praising the action scenes. Zoro is voiced by Kazuya Nakai in the Japanese version of the anime. In the English dubs, he is voiced by Marc Diraison for 4Kids and by Christopher Sabat for Funimation. Sabat's work with Zoro has resulted in him being a nominated of the category "Best Voice Actor (English)" in the Society for the Promotion of Japanese Animation (SPJA) Awards from 2008. Carl Kimlinger from Anime News Network commented on Sabat's work with Zoro as a "standout", noting that Zoro and Sabat are "well-matched. Kimlinger also found that his along with Sanji's flashbacks from the anime "really do jerk tears, even if they are less than gracefully executed".
Source from wikipedia