Alafin of Oyo

Territory located in present-day Nigeria. Since the 1900 political absorption of the kingdom in Northern Nigeria, the traditional monarchy was either a tool of British indirect rule or legally irrelevant within the republic.

In the Yoruba language, the word 'oba' means king or ruler. It is also common for the rulers of the various Yoruba domains to have their own special titles. In Oyo, the Oba is referred to as the Alaafin.

...
Wikipedia