Iyo (伊予国; -no kuni) was an old province of Japan in the area that is today Ehime prefecture on Shikoku. Iyo bordered on Awa, Sanuki, and Tosa provinces.

The ancient provincial capital was near modern Imabari. During the Sengoku period it was split into several fiefs, the largest one usually being run from Matsuyama. It was briefly unified by the Chosokabe clan of neighboring Tosa, but Toyotomi Hideyoshi invaded Shikoku in 1584 and reallocated the fiefs.