The Illanun, called Iranun and Ilianon as well, are closely related culturally and linguistically to the Maranao and Maguindanaon. The Illanun language is part of the Austronesian family that is most closely related to Maranao. When the Spaniards left, however, contact between the Maranao and Illanun decreased.

The majority of Illanun live along the coastline in the of the towns of Nulingi, Parang, Matanog, and Barira in Maguindanao Province, Mindanao; along the Iliana Bay coast, north of the mouth of the Pulangi River; and all the way to Sibugay Bay in Zamboanga del Sur and even the western coastal plain of Borneo. Illanun, a Malay term meaning “pirate,” is appropriate for the people of this ethnic group, who were once regarded as the fiercest pirates in the Malay area.