Michaelnbach is a municipality in the district of Grieskirchen, in the Austrian state of Upper Austria. It is located in the Hausruckviertel region of the state, in the Alpine foothills north of the Hausruck range.
The municipality covers an area of about 23 square kilometres and has a population of roughly 1,300. It is divided into several small settlements and hamlets, with the village of Michaelnbach at its centre. The surrounding landscape is predominantly agricultural, characterised by rolling hills, farmland and patches of woodland.
Michaelnbach lies roughly 10 kilometres west of Grieskirchen, the district's administrative centre, and about 35 kilometres west of Linz, the state capital. It is connected to the regional road network and served by public transport links to the surrounding towns.