Jōnin

are generally highly-experienced ninja with great individual skill who serve as military captains. They are often sent on A-rank missions, and experienced Jonin may even be sent on S-rank missions (which are considered to be the greatest difficulty). They may also carry out these missions alone. They are sometimes assigned as sensei for three-person teams of Genin. It is as of yet unknown what one has to undergo to become one. It is mentioned in the Naruto Anime Profiles databook that Jonin are appointed, however there was mention of a Jonin exam in the Kurama filler arc. It is known that most Jonin are generally able to use at least two types of elemental jutsu.

Becoming a Jonin is the highest level ninja you can become with the exception of being a Kage. Jonin are given very intense and serious missions that most of the time include assassinations. They may carry out these missions alone. When you become a Jonin, you may be assigned three Genin to look over. One part of your duties to help instruct and train these Genin to become great ninjas.

List of Jonin in Naruto
Asuma Sarutobi

Kakashi Hatake

Kurenai Yuhi

List of Jonin in Naruto: Shippūden
Asuma Sarutobi

Kakashi Hatake

Kankuro

Kurenai Yuhi

Neji Hyuga

Temari