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.

In Greek mythology, Aeson was a king of Iolcus in Thessaly. He was the father of the hero Jason. According to one version of the story, he was imprisoned by his half-brother Pelias, and when Pelias intended to kill him he committed suicide. In another story, he was killed by Jason's wife Medea, who brought him back to life as a young man.