Assieu is located some 30 km south by south-east of Givors and 8 km east by north-east of Saint-Maurice-l'Exil. Access to the commune is by the D131 road from the D134 in the south passing north then east in the commune to the town then north and continuing north-west to Route nationale 7. Apart from the town there is the village of La Charinaz in the east and Les Bruyeres in the west. The commune has large forests in the east as well as one in the west with significant residential areas and the rest of the land farmland.[3]
The Vareze river forms the northern border and gathers many tributaries rising in the commune as it flows west to join the Rhône at Saint-Alban-du-Rhône.[3]
^"Répertoire national des élus: les maires". data.gouv.fr, Plateforme ouverte des données publiques françaises (in French). 2 December 2020. Archived from the original on 28 June 2020. Retrieved 7 May 2024.