S=Rank is one of the five classifications. It is preceded by A-rank. It is typically used when classifying techniques intended for highly experienced jōnin and Kage-level shinobi. S-rank techniques are almost always unique to a single user, and as such are trademark abilities of that user.
Missions can also be classified as S-rank, these are the highest paying and most dangerous type of mission a ninja can go on. These missions are exclusively assigned to highly skilled jōnin or large squads of ninja. S-rank missions pay at least 1,000,000 ryō.