Cartimandua or Cartismandua was a 1st-century queen of the Brigantes, a Celtic people living in what is now northern England. She came to power around the time of the Roman conquest of Britain, and formed a large tribal agglomeration that became loyal to Rome. The only account of her is by the Roman historian Tacitus, through which she appears to have been widely influential in early Roman Britain.

The Brigantes were Ancient Britons who in pre-Roman times controlled the largest section of what would become Northern England. Their territory, often referred to as Brigantia, was centred in what was later known as Yorkshire. The Greek geographer Ptolemy named the Brigantes as a people in Ireland also, where they could be found around what is now Wexford, Kilkenny and Waterford, while another people named Brigantii is mentioned by Strabo as a sub-tribe of the Vindelici in the region of the Alps.