The novel concerns the life of Okonkwo, a leader and local wrestling champion throughout the nine villages of the Igbo ethnic group of Umuofia in Nigeria, his three wives, his children (mainly concerning his oldest son Nwoye and his favorite daughter Ezinma), and the influences of British colonialism and Christian missionaries on his traditional Igbo (archaically spelled "Ibo") community during an unspecified time in the late nineteenth or early twentieth century.
It was followed by a sequel, No Longer at Ease (1960), originally written as the second part of a larger work together with Things Fall Apart, and Arrow of God (1964), on a similar subject. Achebe states that his two later novels, A Man of the People (1966) and Anthills of the Savannah (1987), while not featuring Okonkwo's descendants and indeed set in completely fictional African countries, are spiritual successors to the previous novels in chronicling African history.
Okonkwo has risen from nothing to a high position. His father, a lazy flute-player named Unoka, was skilled in the art of conversation, but was an unsuccessful man with regard to material wealth. Through hard work, Okonkwo has risen to a highly regarded position in his society, showing himself to be skilled in battle and earning several titles. He has taken three wives, has several children, and has built substantial wealth through his farming of yams, the staple crop of his villiage. He rules his family with a firm hand and an overbearing demeanor, struggling to demonstrate how he does not have the laziness and weakness that characterized his father.
One day, a neighboring clan commits an offense against Umuofia. To avoid war, a bargain is struck that involves the offending clan releasing to Umuofia a boy, whose name is Ikemefuna, to be sacrificed to the gods, but not immediately. He lives in Umuofia for several years, and during that time he lives under Okonkwo's roof. He becomes like a part of Okonkwo's family. In particular, Nwoye, Okonkwo's oldest son, loves Ikemefuna like a brother. But eventually the Oracle calls for the boy's death, and a group of men take Ikemefuna away to complete the sacrifice. Okonkwo, fearful of being perceived as soft-hearted and weak, participates in the boy's death, despite the advice of the clan elders.
Okonkwo is shaken as well, but he continues with his drive to become a lord of his clan. He is constantly disappointed by Nwoye, but he has great love for his daughter Ezinma, his child by his second wife Ekwefi. Ekwefi bore nine children, but only Ezinma has survived. Ekwefi loves the girl fiercely. Ezinma is sickly, and sometimes Ekwefi fears that Ezinma, too, will die. Late one night, the powerful Oracle of Umuofia brings Ezinma with her for a spiritual encounter with the earth goddess. Terrified, Ekwefi follows the Oracle at a distance, fearing harm might come to her child. Okonkwo follows, too. Later, during a funeral for one of the great men of the clan, Okonkwo's gun explodes, killing a boy. In accordance with Umuofia's law, Okonkwo and his family are exiled to the village of Mbanta for seven years.
During Okonkwo's exile, the white man arrives in both Umuofia and Mbanta. Mr. Brown, a missionary, begins winning converts to Christianity, though generally these are only outcasts or men of low rank. However, with time, the new religion gains momentum. Nwoye becomes a convert after realizing that the new religion will provide him a remedy for the death of Ikemefuna and the twin born children. When Okonkwo learns of Nwoye's conversion, he beats the boy. Nwoye leaves home.
Okonkwo returns to Umuofia to find the clan sadly changed. The church has won some converts, some of whom are fanatical and disrespectful of clan custom. Worse, the white man's government has come to Umuofia. The clan is no longer free to judge its own; a District Commissioner, backed by armed power, judges cases in ignorance.
During a religious gathering, a convert unmasks one of the clan spirits. The offense is grave, and in response the clan decides that the church will no longer be allowed in Umuofia. They tear the building down. Soon afterward, the District Commissioner asks the leaders of the clan, Okonkwo among them, to come see him for a peaceful meeting. The leaders arrive, and are quickly seized. In prison, they are humiliated and beaten, and they are held until the clan pays a heavy fine.
After a release of the men, the clan calls a meeting to decide whether they will fight or try to live peacefully with the whites. Okonkwo wants war. During the meeting, court messengers come to order the men to break up their gathering. The clan meetings are the heart of Umuofia's government; all decisions are reached democratically, and an interference with this institution means the end of the last vestiges of Umuofia's independence. Enraged, Okonkwo kills the court messenger. The other court messengers escape, and because the other people of his clan did not seize them, Okonkwo knows that his people will not choose war. Embittered and grieving for the destruction of his people's independence, and fearing the humiliation of dying under white law, Okonkwo returns home and hangs himself, which is seen as weak and an attack against nature, so much so that others from Umuofia cannot touch his body.
The District Commissioner and his messengers arrive at Umuofia to see Okonkwo dead, and are asked to take down his body since Ibo mores forbid clan members to do this. The Commissioner plans to write a book about his experiences dealing with undignified behavior in the area, titled The Pacification of the Primitive Tribes of the Lower Niger, which might include a small section about Okonkwo.
Ekwefi is Okonkwo's second wife who has had trouble having children. She loves her only child and daughter Ezinma. She was once the most beautiful woman in the village and was at one time married to another man, but she left this man and came to Okonkwo's Obi.
Ikefuma was a young man that was taken from another village to prevent war between the two cities. Ikefuma lived with Okonkwo and his family for three years, becoming very much a part of the family and even referring to Okonkwo as father. Nwoye looked up to him greatly. He was taken out and killed by the men of the village, including Okonkwo, in the novel. He is a Christ figure in the novel and also a symbol of the story of Abraham and Isaac in the novel.
Nwoye is Okonkwo's eldest son. He is not very much like his father and is more interested in the stories his mother tells than in the stories of war. He hates and fears his father, finally leaving to join the church and taking the name "Isaac." He plans to one day come back and save his mother and sisters.
Obierika is Okonkwo's closest friend. He, too, is a warrior, but he begins to question their way of life.
Within forty years of the British arrival, by the time Achebe was born in 1930, the missionaries were well-established. Achebe's father was among the first to be converted in Ogidi, around the turn of the century. Achebe himself was an orphan, so it can safely be said the character of Nwoye, who joins the church because of a conflict with his father, is not meant to represent the author. Achebe was raised by his grandfather. His grandfather, far from opposing Achebe's conversion to Christianity, allowed Achebe's Christian marriage to be celebrated in his compound.
In 1987, the book was made into a very successful mini series directed by David Orere and broadcast on Nigerian television by the NTA (Nigerian Television Authority). It starred movie veterans like Pete Edochie, Nkem Owoh and Sam Loco.