Orochimaru (大蛇丸), featured in the JapanesefolktaleJiraiya Gōketsu Monogatari, is the arch-enemy of the ninjaJiraiya. He was once named Yashagorō (夜叉五郎) and was one of Jiraiya's followers, but he was overtaken by serpent magic. Having changed his name to "Orochimaru", he gained the ability to turn himself into a giant serpent. He attacked Jiraiya and Tsunade and defeated them with his venom (only for another follower to save the couple's lives afterwards). The kanji (大蛇, usually pronounced daija) literally mean "giant snake" or "serpent".
In the popular manga and anime series Naruto, a character called Orochimaru is one of the main antagonists of the series. Tsunade, Jiraiya, and Orochimaru appear as three legendary ninja known as the Sannin. Naruto's Orochimaru can summon snakes into battle, up to and including Kaiju-sized monsters. This summoning ability is predicated on Orochimaru having established a blood-contract with all snake species. Jiraiya and Tsunade can also summon toads and slugs (respectively), and Orochimaru is also capable of transforming into a snake.