Okonkwo is the protagonist of Nigerian writer Chinua Achebe's 1958 novel, Things Fall Apart. The question is often asked if Okonkwo, a member of the Igbo tribe, is a tragic hero, and there are really two answers.

If we look at it from a Greek or Elizabethan perspective, then no, Okonkwo does not fit the definition of a classic tragic hero. The Greeks, in particular, had a narrow understanding, as laid out in Aristotle's Poetics, of what a tragic hero is. What Oknokwo does share with heroes like Oedipus or Hamlet is that he is representative of his community, elevated within his community (he's a famous wrestler), and has a tragic flaw which brings about his fall. Pride or hubris is a quality many tragic protagonists share, and Okonkwo is bursting with pride. He's a successful and prominent member of his tribe, but he's also angry, violent, arrogant, and abusive of his wives and children. He's eventually expelled from his community for breaking the tribe's rules.

Again, from a classical perspective, the book does not qualify as a tragedy. But I think there's a strong case to make that it is a contemporary tragedy. The tragedy works on two levels. Okonkwo's arc is similar to that of other heroes, as he goes from high status to expulsion and exile to death by suicide. Whether the reader experiences the catharsis expected of a tragedy is, of course, subjective.

On another level, Things Fall Apart is the tragedy of an entire people as, in the second part of the book, white Westerners arrive and, with them, Christianity, capitalism, and colonialism. The Igbo will have their culture destroyed, their lands pillaged, and their religion mocked, as will much of the continent. Colonialism is a tragedy for all those who experienced it, all the more so because it was presented by Europeans as a positive force.

Is Okonkow a tragic hero in Things Fall Apart? CRITERIA OF A TRAGIC HERO

If you look over Okonkwo's actions, it can sometimes be difficult to look past his immense insecurity to his also immense pride but it is there.  His absolute unwillingness to listen to others, including dear friends, is part of what leads to his fall, something that tragic heroes often share.

He is also one that rises to a position of nobility prior to his fall as he is accorded great respect as a man with many wives, titles, and an incredibly strong warrior both in battle and in the wrestling ring.

His suffering is also meaningful, though it might not be cathartic in the story, his story itself carries great meaning as a metaphor for the life of the Ibo tribes in Nigeria.

In Things Fall Apart by Chinua Achebe, how might Okonkwo be considered a tragic hero?

Aristotle says that the tragic hero is any protagonist who meets his or her downfall "through some combination of hubris, fate, and the will of the gods" ("Aristotle on Tragedy," paragraph 1). 
If we suspend a postcolonial reading of Things Fall Apart to substitute an Aristotelian reading, we may consider Okonkwo the tragic hero of the piece.

Okonkwo's hubris is integral to his role in Igbo society. He lives his life to prove that he is a strong man, unlike his father, whose memory is a constant humiliation. Okonkwo mistreats anyone he sees as weak, including his own family members. He favors his captured son, Ikemefuna, over his biological son, because he considers Ikemefuna to be more manly. This does not stop Okwonko from sending Ikemefuna to be murdered as a retributive killing. His fear of being thought weak compels him to follow through, no matter how fond he is of the boy.

There are a few instances where the hand of fate governs Okonkwo's downfall. The primary crisis comes when the white man brings their customs and religion to the region. Okwonko's reaction is to fight back, but he finds that not everyone feels the same. The social codes he has dedicated his life to are coming apart before his eyes, as if he has been living a lie. The world as it was no longer exists, and he cannot live in the world that it is becoming. His only option is to kill himself, though he knows this act is forbidden by the gods. There is a sense that Okonkwo was backed into a corner by circumstance and could not escape this fate, making him a tragic hero.