Iwashiro Province (岩代国 Iwashiro-no kuni) is an old province in the area of Fukushima Prefecture. It was sometimes called Ganshū (岩州).
The province occupies the western half of the central part of Fukushima Prefecture; the eastern half is Iwaki Province. More precisely, Date and Adachi districts in the north belong to Iwashiro and Higashishirakawa and Nishishirakawa districts in the south belong to Iwaki. The border between the two provinces is the Abukuma River. The former ichinomiya of the province is Isasumi Shrine.
- On December 7, 1868, the province was formed out from Mutsu Province. As of 1872, the population was 427,933.
- Fukushima Prefecture
- Aizu Region, Fukushima
- Nakadōri Region, Fukushima