Isiolo District was an administrative district in Eastern Province of Kenya, with its capital at Isiolo town.
In 1934, the Samburu would be transferred to the Rift Valley Province.
The total population of the two districts stood at 143,294 as per the 2009 census.
This effectively led to the creation of Isiolo County.
The district was divided into six administrative divisions: Central, Garba Tula, Kinna, Merti, and Sericho.