Hunnum (also known as Onnum, and with the modern name of Halton Chesters) was a Roman fort on Hadrian's Wall located north of the modern-day village of Halton, Northumberland in North East England.

The site of the fort is bisected by the B6318 Military Road, which runs along the route of the wall at that point.

These alterations were probably due to the replacing of the original part-mounted garrison by Ala I Pannoniorum Sabiniana, the first cavalry regiment on the Wall which would have required more barracks and stables than the original part-mounted garrison, which the south-western extension of the fort would have provided.

A dedicatory slab from the west gate of the fort tells us that the Legio VI Victrix were responsible for the initial building work.

The field north of the Military Road containing the northern section of the fort was first ploughed in 1827, and a fine bath-house was found.