Oedipus is considered to be the prime example of a tragic hero, especially as defined by Aristotle. According to Aristotle's definition, a tragic hero must be of high status and be a noble and admirable person, but must also have a character flaw that propels him or her to his or her great fall. Oedipus's character flaws are his excessive pride and his naivete. While Oedipus can be recognized as a noble and virtuous person for caring for his citizens, his naivete also contributes to both the city's plague and his own downfall. Therefore, Oedipus can actually be considered both a hero and a naive fool.
We especially see Oedipus's noble and virtuous nature at the beginning of the story when we see his compassion for his people and his willingness to do whatever is needed to end the suffering his citizens are enduring due to the plague. Oedipus states that his citizens' agony is causing him even greater agony, as we see in his lines:
My poor children, what you desire is known and not unknown to me, for I see well that everyone is sick, and being sick, still, not one of you is as sick as I am. (63-66)
In other words, Oedipus is stating that he is even more sick at heart than his citizens due to their sickness and suffering. We also learn in this speech that he has "been weeping much" and racking his brain to find a solution and, therefore, has sent Creon to Apollo's oracle at Delphi to learn what should be done to end the plague (71). Oedipus's compassion and willingness to help shows us what a noble and heroic ruler he is towards his citizens.
However, unfortunately, Oedipus is too blind to realize that his own transgressions are the cause of his people's suffering. As Tiresias phrases it, Oedipus is blind. Oedipus is particularly blind, naive, and stubborn in believing that Creon and Tiresias are conspiring against him to take the crown. Oedipus was even blind in failing to realize when he was younger that the man he killed at the crossroads leading towards Delphi could possibly have been his father. Hence, both of these instances serve to prove that while Oedipus is a hero, he is a naive, foolish, tragic hero.