The correct answer is protectorate.
Protectorate is the relationship between two states in which one state exercises some or partial control over the other, weaker one.
The protectorate is usually established by treaty. The weaker nation surrenders the management of the country's most important issues to the greater sovereign state. The state under protectorate loses some of its powers but remains independent and with local autonomy.
Protectorates differ from colonies as they have their own local rulers and the country remains sovereign. They have direct foreign relations only with the protecting power, meaning other states have to approach the protector first in order to deal with the protectorate's foreign affairs.
