A Protectorate is a nation which lives under the protection or control of a more powerful nation.
The Evora Homeworld and Haven are both protectorates of the United Federation of Planets. (Template:Titles/Star Trek: Insurrection), (TNG: "Haven").
Raatooras, an Arin'Sen colony was a protectorate of the Klingon Empire before the planet was abandoned. (ENT: "Judgment")