Kathiri, officially the Hadhrami Kathiri Dynasty in Seiyun or the Sultanate of Seiyun, was a sultanate in the Hadhramaut region of the southern Arabian Peninsula, in what is now part of Yemen and the Dhofari region of Oman.

Sultan is a position with several historical meanings. Originally, it was an Arabic abstract noun meaning "strength", "authority", "rulership", derived from the verbal noun سلطة sulṭah, meaning "authority" or "power". Later, it came to be used as the title of certain rulers who claimed almost full sovereignty without claiming the overall caliphate, or to refer to a powerful governor of a province within the caliphate. The adjectival form of the word is "sultanic", and the state and territories ruled by a sultan, as well as his office, are referred to as a sultanate.