third largest cultural-linguistic group in the Philippines. When discovered by the Spanish in the 16th century, they occupied the narrow coastal plain of northwestern Luzon, known as the Ilocos region. The growth of their population later led to much migration to neighbouring provinces, as well as to Mindanao and Hawaii. Their language is closely related to others of northern Luzon, all of which belong to the Austronesian (Malayo-Polynesian) family of languages. The Ilocano (Iloko) language in the late 20th century was spoken by about 6,850,000 persons.

The major Ilocano provinces, Ilocos Norte, Ilocos Sur, and La Union, are among the most densely populated areas in the Philippines. Rice is the staple crop, grown on small fields and irrigated by rainfall during the rainy season. Vegetables and pigs, goats, and chickens are also raised. Tobacco is an important cash crop. Many Ilocano supplement their incomes by wage work or handicrafts.

The wealthier families generally reside in the cities and towns. Marriages are usually arranged so as to maintain class lines, the husband's family providing the sabong, or dowry of land. Most of the people are Roman Catholic.