Osimo is a town and comune of the Marche region of Italy, in the province of Ancona.

The municipality covers a hilly area located approximately 15 kilometres (9.3 mi) south of the port city of Ancona and the Adriatic Sea.

Vetus Auximum was founded by the same Greek colonists of Ancona; later it was contested by the Gauls and the Picentes until conquered by the Romans, who used it as a fortress for their northern Picenum settlement starting from 174 BCE.

Inscriptions and monuments in its town square attest to the importance of Osimo during imperial times.

[3] In the 6th century it was besieged twice in the course of the Gothic War (535–554) by Belisarius[4] and Totila; the Byzantine historian Procopius said it was the leading town of Picenum.