Governor

From Halopedia, the Halo wiki

Template:Ratings Governor is a position that can be held by a human. The Governor is basically the leader of the part of a planet or (back then in the Halo universe) in districts or states.[1]

The only known human governor is Nils Thune of the planet Harvest.[2]

Presumably, the leader of a group such as the Governors of Contrition would also be known as "governor".

Sources