One night, all the animals at Mr. Jones' Manor Farm assemble in a barn to hear old Major, a pig, describe a dream he had about a world where all animals live free from the tyranny of their human masters. old Major dies soon after the meeting, but the animals — inspired by his philosophy of Animalism — plot a rebellion against Jones. Two pigs, Snowball and Napoleon, prove themselves important figures and planners of this dangerous enterprise. When Jones forgets to feed the animals, the revolution occurs, and Jones and his men are chased off the farm. Manor Farm is renamed Animal Farm, and the Seven Commandments of Animalism are painted on the barn wall.

Initially, the rebellion is a success: The animals complete the harvest and meet every Sunday to debate farm policy. The pigs, because of their intelligence, become the supervisors of the farm. Napoleon, however, proves to be a power-hungry leader who steals the cows' milk and a number of apples to feed himself and the other pigs. He also enlists the services of Squealer, a pig with the ability to persuade the other animals that the pigs are always moral and correct in their decisions.