The Cantiaci or Cantii were a group of people from the Iron Age who spoke Celtic languages and lived in Britain before the Romans arrived. They gave their name to a region in Roman Britain. They lived in the area now known as Kent, in the southeast part of England. Their main city was called Durovernum Cantiacorum, which is now known as Canterbury.

The Cantiaci lived next to the Regni people to the west and the Catuvellauni people to the north.

Julius Caesar arrived in the area called Cantium in 55 and 54 BCE during the first Roman attempts to reach Britain. He wrote about this in his book called De Bello Gallico, chapter 14.

Rulers

Julius Caesar recorded the names of five Celtic tribes living in the area that would later become the main region of the Catuvellauni: the Ancalites, the Bibroci, the Cassi, the Cenimagni, and the Segontiaci. Each tribe had its own leader, called a "king" or chieftain. Caesar noted that their lifestyle was similar to the Gauls, their close relatives in France. The Roman invasion of Britain may have been influenced by the Britons sending weapons to the Gauls, who were being controlled by the Romans.

Caesar wrote about four leaders—Segovax, Carvilius, Cingetorix, and Taximagulus—who ruled in the region of Cantium during his second visit to Britain in 54 BCE. At that time, the British leader Cassivellaunus, who was under siege in his fortress north of the Thames River, sent a message to these four kings. He asked them to attack the Roman camp to distract the enemy. The attack did not succeed, a chieftain named Lugotorix was captured, and Cassivellaunus had to agree to negotiate with the Romans.

Between Caesar’s visits and the Roman conquest of Britain under Emperor Claudius in 43 CE, British kings began making coins with their names stamped on them. Some of the known rulers of the Cantiaci tribe include:

According to Nennius, a medieval writer, Gwrangon was the king of Kent during the time of Vortigern. However, Vortigern took control of the kingdom and gave it to Hengist. Nennius is not considered a reliable source, and Gwrangon is believed to have been moved by the storyteller from the region of Gwent to Kent. The story suggests that Gwrangon secretly gave his kingdom to Hengist, whose daughter Vortigern wanted to marry.