Ermenguer was the first known ruler of the county of Empúries (813-817, attested).
It seems that he was a Goth, a member of the local nobility. He was given the county when the region was stabilised under the Franks, but it was given to Gaucelm, count of Roussillon, four years later.
Ermenguer led a local fleet that, in 813, sailed to the Balearic Islands, then under the Moors. After a truce with the Muslims, Andalusian ships ravaged Corsica and Sardinia (813), but when they returned, they were surprised by Ermenguer and defeated. Five hundred Christian prisoners were liberated.