The current municipality of Patras was formed at the 2011 local government reform by the merger of 5 municipalities that made up the Patras Urban Area.

From 2011 on, can data also reflect the city's urban area population, as all the municipalities that made up the Patras Urban Area were joined to create the new larger Patras municipality, formed at the 2011 local government reform.

The municipality Marathon was formed at the 2011 local government reform by the merger of the following 4 former municipalities, that became municipal units:

The municipality Distomo-Arachova-Antikyra was formed at the 2011 local government reform, according to the programme Callicrates, by the merger of the following 2 former municipalities of Arachova and Distomo and from the former community Antikyra, that became municipal units: