Iolcus is an ancient city, a modern village and a former municipality in Magnesia, Thessaly, Greece. Since the 2011 local government reform it is part of Volos, of which it is a municipal unit. It is located in central Magnesia, north of the Pagasitic Gulf. Its land area is 1.981 km2. The municipal unit is divided into three communities, Agios Onoufrios, Anakasia and Ano Volos, with a total population of 2,008. The seat of the former municipality was the village of Ano Volos.

Magnesia is one of the regional units of Greece. It is part of the region of Thessaly. Its capital is the city of Volos. About 70% of the population of Magnesia live in the Greater Volos area, which is the second-largest city in Thessaly and the third busiest commercial port in Greece.