Kage

is a title reserved for the leader of one of the Five Great Shinobi Countries' hidden villages. They are collectively known as the. A Kage oversees the activities of their village, from sending ninja on missions to making the hard decisions regarding the safety of their people. A village's Kage is generally acknowledged as its most powerful ninja.

Background
The title was originally created by Hashirama Senju soon after the formation of Konohagakure, making him the first Kage to exist after being elected by the population of his village and country. After the creation of the position, other nations praised the innovative system that had been created and soon began to imitate.

Overview
Each village has its own name for its Kage: As a Kage's primary concern is their village, interaction between the Kage is rare; only during treaty-signing ceremonies or shared public events has a Kage been seen to interact with one of his or her peers. The only time that all five Kage are together is during a Kage Summit, which can be convened by any of the five to discuss topics that apply to all of their villages.
 * The of Konohagakure.
 * The of Sunagakure.
 * The of Kirigakure.
 * The of Kumogakure.
 * The of Iwagakure.

How a Kage is appointed appears to differ from village to village. In Konoha, the Hokage typically appoints their successor. If the Hokage dies or is otherwise incapacitated before they can choose a successor, the selection falls to the Land of Fire's daimyō who is advised by his committee as well as the village's elders, the Jōnin Commander and a representative of the Anbu. This appointment must then be approved by Konoha's jōnin. In Kumo, after the Third Raikage died, his son automatically became Fourth Raikage, a decision made many years earlier. If a Kage should ever choose to retire they will keep their title for the rest of their life, and can assist the new Kage with decision-making and other responsibilities. A retired Kage can even return to full-time leadership if their successor dies, as the Third Hokage did when the Fourth Hokage gave his life to save Konoha, being unable to find anyone both suitable and willing to take on the title of Fifth Hokage at the time.

Because jinchūriki were so important to their village, it was a tradition for a jinchūriki to be a relative of the current Kage, both to strengthen the jinchūriki's loyalties to the village and to display the Kage's might. For example, Killer B is the adoptive brother of the Fourth Raikage and Gaara is the son of the Fourth Kazekage.

Trivia

 * The Third Hokage was considered to be the strongest of the Five Kage of his time. Years later, the Seventh Hokage was also recognised in the same way.
 * In the anime, the Village Heads of Amegakure, Takigakure and Kusagakure, are acknowledged as Kage. Hoshigakure has unofficially dubbed each of its leaders the, signifying their ambition for Hoshigakure to be recognised as an equal to the hidden villages of the Five Great Shinobi Nations. Therefore, Hoshikage can be considered as a pseudo-kage.
 * In Jiraiya's novel The Tale of the Utterly Gutsy Shinobi, the village leader of Shuku is called the Kokage as an obvious homage to the Hokage position.
 * In the anime, according to Hashirama's account, soon after the creation of the title Hokage came the Raikage, Tsuchikage, Mizukage and Kazekage.