margrave; marquis
A historical European noble title for a lord ruling a border territory (march). In some contexts, it can correspond to 'marquis' in English, but the primary meaning is 'margrave'.
In medieval Europe, margraves played an important role in defending the borders.
ブランデンブルク辺境伯は、後にプロイセン王国の基礎を築いた。
The Margrave of Brandenburg later laid the foundation for the Kingdom of Prussia.