Queen Boudica of the Iceni!

In stature she was very tall, in appearance most terrifying, in the glance of her eye most fierce, and her voice was harsh; a great mass of the tawniest hair fell to her hips; around her neck was a large golden necklace; and she wore a tunic of divers colours over which a thick mantle was fastened with a brooch. This was her invariable attire ...
— Dio

 Queen Boudica is famous, particularly in Britain, as the warrior queen who nearly drove the Romans from Britain while they were at the height of their power. 

The Wickham Market Hoard: 840 gold Iceni coins.  (Portable Antiquities Scheme from London, England -  Uploaded by Victuallers, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=10731055)

The Wickham Market Hoard: 840 gold Iceni coins.  (Portable Antiquities Scheme from London, England -  Uploaded by Victuallers, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=10731055)

She was wife of Prasutagus King of the Iceni, a wealthy tribe who lived on fertile farmland in the Eastern county now called Norfolk. They seem to have been a religious tribe. Hoards of 800 or more gold coins have been found buried in Norfolk as gifts to the gods. These coins frequently feature pictures of beautiful horses, a symbol of the horse goddess Epona. The Iceni were living on a direct trading/religious route with the Isle of Mona (Angelsey) stronghold of the druids and a source of gold. 

So how did Boudica move from wealthy chieftan's wife to rebel warrior? After the Roman invasion in AD43, Prasutagus, made an agreement with the Romans that he would be allowed to remain King until his death. Only then would his land be swallowed up into the new Roman province. One other king, Togidobnus of the Regni, was allowed to do this as well.

When Prasutagus died, however, he left half his kingdom to his two daughters and half to the Roman Emperor Nero. Perhaps he was hoping the gesture would soften Nero. Well, he thought wrong. The Romans completely ignored his will. What more proof did the Romans need of the uncivilized nature of the Celts than the fact that they'd leave a kingdom to women? 

The Romans did not recognize Boudica or her daughters' claim to the throne. They marched into Iceni territory and stole Prasutagus' land and money. They claimed he owed them money/taxes then they enslaved his family, whipped Queen Boudica and assaulted her daughters.

(His) kingdom was plundered by centurions, his house by slaves, as if they were the spoils of war. First, his wife Boudicea was scourged, and his daughters outraged. All the chief men of the Iceni, as if Rome had received the whole country as a gift, were stripped of their ancestral possessions, and the king’s relatives were made slaves...

Boudica was understandably angry. It's been suggested that the reason Prasutagus didn't leave his kingdom to his wife was that he knew she already hated the Romans. Well, now she had even more reason. She began a revolt and none of the Celtic warriors had any problem with following a woman into battle.

Joining up with the local Trinovantes tribe, Boudica waited until the Roman Governor, Gaius Suetonius Paulinus, was attacking the Isle of Mona, now Anglesey, a druid stronghold. He and his troops wanted to wipe out the druids (considered the driving force of British resistance against Roman rule) and dig up all the oak trees in the country's most sacred sanctuary. Maybe this attack on the keepers of Celtic laws, culture and religion made Boudica even more determined.

The head of a statue of Claudius found in Suffolk, believed to have been taken from the Temple of Claudius during Boudica's revolt. By Michel Wal ((own work)), CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6496434

The head of a statue of Claudius found in Suffolk, believed to have been taken from the Temple of Claudius during Boudica's revolt. By Michel Wal ((own work)), CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6496434

She raised an army of up to 125,000 fighters and marched on Camulodunum, the former capital of the Trinovantes tribe (now called Colchester.) It was being used as a new colonial town for Roman veterans and was home to a much hated temple to Claudius, which had been built with Celtic taxes. The Iceni and Trinovantes destroyed the town and the temple. It is said they killed everyone in their path.

Then Boudica headed for Londonium (London.) Suetonius had already arrived back at the city, but realizing he didn't have enough troops to defend it, he ordered an evacuation of his troops leaving the civilians to fend for themselves. Boudica burnt London to the ground. The flames were so intense that there's still a layer of burned material that can be found during excavations in London bearing witness to the destruction.  70,000 people were killed. The Celtic troops moved on to Veralanium (St Albans) and destroyed that too.

It's possible Boudica was making her way back to Iceni territory, but by this time her warriors were a little out of control and maybe too confident. Eventually her troops and Suetonius's men had to meet up. No one is quite sure where her last battle happened, but the element of surprise was lost. Suetonius was able to meet the Celts in a standard pitched battle format and the Celts were defeated. It is said that 15,000 Romans killed up to 80,000 Celts.

Tacitus says Boudica poisoned herself rather than be taken prisoner by the Romans. 

Boudica is a national hero in Britain.

Statue of Boudica and her daughters near Westminster Bridge, London. This Victorian statue is not very accurate regarding her clothing, the chariot etc.  (By No machine-readable author provided. Lily15 own work assumed (based on copyright claims), CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1601437)

Statue of Boudica and her daughters near Westminster Bridge, London. This Victorian statue is not very accurate regarding her clothing, the chariot etc.  (By No machine-readable author provided. Lily15 own work assumed (based on copyright claims), CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1601437)