The Ileksa (Russian: Илекса) is a river in Onezhsky District of Arkhangelsk Oblast and Pudozhsky District of the Republic of Karelia in Russia.

The main tributary of the Ileksa is the Chusreka (left).

Almost all of the valley of the Ileksa belongs to the Vodlozersky National Park, shared by Arkhangelsk Oblast and the Republic of Karelia.

The park was established in 1991 to protect the taiga, coniferous forests.

Since 2001, the National Park has the status of the UNESCO Biosphere Reserve, the first one in Russia.