Acerrae (Ancient Greek: Ἀχέρραι) was a city of Cisalpine Gaul, in the territory of the Insubres.
Polybius describes it merely as situated between the Alps and the Po; and his words are copied by Stephanus of Byzantium: but Strabo tells us that it was near Cremona: and the Tabula places it on the road from that city to Laus Pompeia (Lodi Vecchio), at a distance of 22 Roman miles from the latter place, and 13 from Cremona.
These distances coincide with the position of Gherra or Gera, a village, or rather suburb of Pizzighettone, on the right bank of the river Adda.
It appears to have been a place of considerable strength and importance (probably as commanding the passage of the Adda) even before the Roman conquest: and in 222 BC, held out for a considerable time against the consuls Marcellus and Scipio, but was compelled to surrender after the Battle of Clastidium.
Gnaeus Cornelius Scipio Calvus and Marcus Claudius Marcellus).