tetrarch

Definition

A tetrarch was a governing official who ruled over a division of the Roman Empire. Each tetrarch was under the authority of the Roman emperor.

The title "tetrarch" comes from the fact that each tetrarch ruled over one of four divisions.
Each division covered one or more provinces, such as Galilee or Samaria.
"Tetrarch" could also be translated as "ruler" or "governor."