The name of the city is believed be a variation of Kānh-pur, meaning "town of Kānh or Krishna". Other theories are that the name is derived from Karnapur (meaning "town of Karna", one of the heroes of the Mahabharata), or that it came from the nearby town of Makanpur, earlier known as Khairabad, where the Sufi saint of the Madariya Sufi order, Badiuddin Zinda Shah Madar, settled.
In 2018, Kumpur, was considered by the World Health Organization as the world's most polluted city.
In the 19th century, Cawnpore was an important British garrison with barracks for 7,000 soldiers. During the Indian Rebellion of 1857, 900 British men, women and children were besieged in the fortifications for 22 days by rebels under Nana Sahib Peshwa. They surrendered on the agreement that they would get safe passage to the nearby Satti Chaura Ghat whereupon they would board barges and be allowed to go by river to Allahabad.
Though controversy surrounds what exactly happened at the Satti Chaura Ghat, and who fired the first shot, it is known that, soon afterwards, the departing British were shot at by the rebel sepoys and were either killed or captured. Some of the British officers later claimed that the rebels had, on purpose, placed the boats as high in the mud as possible, to cause delay. They also claimed that Nana Sahib's camp had previously arranged for the rebels to fire upon and kill all the English. Although the East India Company later accused Nana Sahib of betrayal and murder of innocent people, no evidence has ever been found to prove that Nana Sahib had pre-planned or ordered the massacre. Some historians believe that the Satti Chaura Ghat massacre was the result of confusion, and not of any plan implemented by Nana Sahib and his associates. Lieutenant Mowbray Thomson, one of the four male survivors of the massacre, believed that the rank-and-file sepoys who spoke to him did not know of the killing to come.