Tana River County is named after the Tana River, the largest river in Kenya. It has an area of 35,375.8 square kilometers (13,658.7 sq mi) and a population of 240,075. The capital and largest town is Hola, sometimes known as Galole.
The major ethnic groups are the Pokomo, many of whom are farmers, and the Orma, Wardey and Gadsan. The county is generally dry and prone to drought. Rainfall is erratic, with rainy seasons in March–May and October–December. Flooding is also a regular problem, caused by heavy rainfall in upstream areas of the Tana River.
Tana River County comprises several areas of forest, woodland and grassland.