Mr. Jones, the owner of the Manor Farm, has fallen asleep as a result of his drunkenness. All the animals in the farm, at the invitation of the Old Major, assemble for deliberation of the challenges that they face daily in the hands of their human keepers. Old Major delivers a terrific political speech stating unequivocally that they are worse off under the leadership of humans than they would be when they rule among themselves. The Old Major drops the bombshell there is a need for them to rebel against the tyranny of their human leaders. To convince the animals to adopt his position, the Old Major informs the animal about his dream concerning a future world without humans. Besides, he teaches them a song about "Beasts of England." The animals sing this song until they wake up the sleeping Mr. Jones, who fires his gun thinking that there is a fox that has invaded his farm. The animals are dispersed by the shot, and each of them goes to sleep.
When Old Major dies, the animals gather and plan for the rebellion. The animals have spent most of their days deliberating upon then best approaches that would give them a win. However, the date or timing of the rebellion remains unclear. The pigs are the most intelligent animals on this farm. Thus, it is only fair that they take charge of the planning of the rebellion. Besides, the pigs are responsible for educating the other animals concerning Animalism, the philosophy that Old Major had introduced before he died. In the group of pigs, Napoleon and Snowball appear like the persons around which all the plans are made. The two would later become fierce rivals after the rebellion. Despite the numerous challenges that exist, the pigs have been immensely successful in teaching the animals about animalism as well as preparing them for the rebellion plans.
When Rebellion occurs, this time, again, Mr. Jones is asleep. He has forgotten to feed the animals. The animals invade the feeds store in search of food. Soon, Mr. Jones arrives to find the looting taking place. He, together with his men, resort to whipping the animals. The animals turn against Mr. Jones and his people. Having been overpowered by the animals, Mr. Jones and his people leave the farm. The triumphant defeat of Mr. Jones is marked with feats. The animals eat heartily and enjoy the moment. After touring the house in which Mr. Jones lived, the animals opt against destroying it, instead reserving it as a monument. Snowball changes the sign "Manor Farm" and makes it "Animal Farm." On the walls of the barn, Snowball paints the Seven Commandments that are supposed to guide the conduct of all the animals on the farm. As a token of appreciation to the efforts of all the animals, the cows give milk, five buckets of it, but Napoleon steals it.
The summer is already ended, and the news of the rebellion in the Manor farm is spreading very fast. The pigeons that have been released by Napoleon and Snowball have facilitated the spreads of this news to other farms. Meanwhile, Jones is seated at a bar enjoying his usual drinks. In October, Jones and a group of other men raid the farm with an idea of trying to regain control over it. However, Snowball shows that he is a master tactician when, with the help of other animals, they successfully repulse the attacks from the humans. The victory provides the animals to celebrate yet another victory against the humans in what they call "The Battle of the Cowshed." Winter had come, and the animals are at the farms working. However, it has become apparent that Mollie is quickly losing interest working in the farm. With time, Mollie works very little and has become less productive. In the long run, Clover realizes that Mollie is being lured by Pilkington to go and work for him. Mollie has been induced by material gains to go and work for Pilkington. Eventually, the Animal Farm loses Molly to Pilkington's farm. As Mollie disappears, the pigeons come back with a report that Mollie has been seen standing by a pub and he wearing the ribbons that he had coveted so much.
The pigs have become extremely powerful over the other animals. They make all the policies and laws which they take to the animals for ratification by way of a vote. However, the animals have no other option but to vote in favor of the new policies. Meanwhile, Snowball and Napoleon have not ceased their arguments. One of the most divisive debates concerns building a windmill on a knoll. Snowball is in support of the mill as he argues that it will save on effort and time. On the other side, Napoleon argues against the mill saying that it will take away much of the labor that will be required in food production during its construction. Napoleon and Snowball also disagree on whether it would be prudent to have an armory of guns or use pigeons to send out the news of rebellion to the other farms. On Sunday when animals are to vote concerning the windmill, Napoleon frustrates the voting by sending his nine dogs to chase Snowball out of the farm. From this day, Napoleon gives a decree stopping all the debates and then goes ahead to create new rules that would guide the farm.
The following year, all the animals dedicate their energy and time to the building g of the windmill. The process is quite tedious and demands all the animals to give the best of their effort and concentration. Boxer emerges as one of the most dedicated and strong animals in the building. Napoleon announces that the Animal Farm is to start trading with the other farms. To facilitate this process, Napoleon hires Mr. Whymper to be his agent. When the humans meet in the pubs, they discuss that the windmill will eventually collapse and the Farm will go broke. By this time, Jones has given up on his attempt to regain control of the farm, and he relocates to another part of the country. The pigs get into the farmhouse and start sleeping on the beds. When questions arise, Squealer justifies the action by saying that the pigs need good rest after a long day's work. During November the same year, a storm blew away the windmill just as the humans had indicated. Napoleon indicates that the disaster has been caused by Snowball. He offers anybody sums of money to any person who will kill Snowball or bring him back to Napoleon alive.
On a day in spring, Napoleon summons all the animals to a meeting. During this meeting, he calls upon all the animals that had appeared to go against his wish from the beginning. They include four pigs and three hens. Napoleon orders his dogs to murder the animals. During the same meeting, many other animals also confess to crimes which they believed were instigated by Snowball. Eventually, Napoleon outlaws sing the song "Beasts of England," and then he replaces it with one that the pig-poet, Minimus, has created. However, the animals do not find the song to be as meaningful as the previous song.
Squealer has come up with statistics intended to back up the increase in food production in the farm. In spite of these statements, the events from the following year indicate that a lot of people are working hard yet the food rations are continuing to decrease. In these circumstances, it could be difficult to justify the increase in productions, unless some pigs are stealing or hoarding the food. Meanwhile, Napoleon is becoming more powerful as time advances. He has suddenly disappeared from the public, instead of letting Squealer to do most of the interaction with the public. Napoleon, again, does not hesitate to execute the individuals whom he things are threats to his rule.
As the years pass, the Animal Farm undergoes a lot of changes. Many animals such as Muriel, Bluebell, Jessie, and Pincher have died. Jones too has died in a far-away land. Clover is 14 years old but has not retired as per the regulations. The number of animals on the farm is also increasing rapidly. Besides, the authority has acquired additional parcels of land from Pilkington, thereby increasing the size of the farm. Through the hard work of the pigs, the farm has constructed a second windmill for milling corn. However, the food is still little, and the animals are suffering, except the pigs.