The ancient Roman and Byzantine empires had well-developed associations, known as demes, which supported the different factions (or teams) to which competitors in certain sporting events belonged, especially in chariot racing. There were initially four major factions in chariot racing, differentiated by the colour of the uniform in which they competed; the colours were also worn by their supporters. The demes had become a focus for various social and political issues for which the general Byzantine population lacked other forms of outlet. They combined aspects of street gangs and political parties, taking positions on current issues, including theological problems and claimants to the throne.

In 531 some members of the Blues and Greens were arrested for murder in connection with deaths during rioting after a chariot race. The murderers were to be executed, and most of them were. On January 13, 532, an angry crowd arrived at the Hippodrome for the races. The Hippodrome was next to the palace complex, so Justinian could preside over the races from the safety of his box in the palace. From the start, the crowd hurled insults at Justinian. By the end of the day, at race 22, the partisan chants had changed from "Blue" or "Green" to a unified Nίκα ("Nika", meaning "Win!", "Victory!" or "Conquer!"), and the crowds broke out and began to assault the palace. For the next five days, the palace was under siege. Fires started during the tumult destroyed much of the city, including the city's foremost church, the Hagia Sophia (which Justinian would later rebuild).

The Nika riots are often regarded as the most violent riots in the city's history, with nearly half of Constantinople being burned or destroyed and tens of thousands of people killed.