The Mbagathi River is a river in Kenya near Nairobi It is a tributary of the Athi River.[1] It forms the southern boundary of Nairobi National Park.[2] Herds of animals cross the river when migrating.It also forms the eastern boundary of Nairobi county passing through Utawala, between Kamulu and Joska[3] A number of small dams have been built along the river.[4]