It is situated by the Bothnian Bay, at the mouth of river Iijoki, and it is part of the Northern Ostrobothnia region.

The city has ambition to become the first zero waste town in the world, and its municipal manager claims that it does not use fossil fuels for energy.

The original name of the settlement was Iijoen kylä, first mentioned in 1374 as Yioki when it was a chapel community within the Pedersöre parish.

The parish of Ii was originally larger than the modern municipality: it included Pudasjärvi and Taivalkoski until 1639, Kiiminki, Ylikiiminki and Haukipudas until 1858.

Finnish (suomi), Swedish (ruotsi) and Sami (saame) count as indigenous languages as they have official status in the country.

For languages with fewer than 10 speakers, the figure is hidden by Statistics Finland due to confidentiality reasons.