Aizu (会津) is the westernmost of the three regions of Fukushima Prefecture, Japan, the other two regions being Nakadōri in the central area of the prefecture and Hamadōri in the east.

It was composed of five districts of Shirakawa (白河), Iwase (石背), Aizu (会津), Asaka (安積) and Shinobu (信夫).

The area encompassed by the province reverted to Mutsu some time between 722 and 724.

[4] Following the Meiji restoration, it became part of the short-lived Iwashiro Province before becoming a region of Fukushima Prefecture.

Although never an official province in its own right, Aizu has a very strong regional identity.