[2] Initially Mombasa was one of the districts of Kenya until 2013 when it was reconstituted as a county, on the same boundaries.

It is the smallest county in Kenya, covering an area of 229.7 km2 excluding 65 km2 of water mass.

Administratively, the county is divided into seven divisions, eighteen locations and thirty sub-locations.

It is situated in the southeast of Coast Province, and the smallest in size, covering an area of 212.5 km2.

The highest point is at Nguu Tatu hills in the mainland north that rises up to 100 m above sea level.