Question: is sannin a ninja rank?
Answer: This title is merely a class rather than an actual rank; the ninja's official rank with a village will usually still be Jounin. ... One group of ninja who have gained this special status are the Sannin, or "Legendary Three Ninja" of Konoha: Jiraiya, Orochimaru, and Tsunade. Most Kage also tend to be in this class.