Answer:
Yes and no. According to the original meaning of the word, Theban King Oedipus was a tyrant. Originally, a tyrant seized power illegally. That's what Oedipus did by killing his father and his sovereign, Theban King Laius. He didn't know whom he was killing when he responded with violence to violent behavior by a stranger who was old enough to be his father and whom he resembled. But the fact remained that he committed murder and didn't go through the necessary cleansing of required purification ceremonies. So his rise to power was illegal in Thebes.
But according to the modern definition, Oedipus may not have been a tyrant. He didn't appear to be viewed as arbitrary, cruel or selfish by his subjects. Instead, he appeared to have gained the love and respect of the Theban people. In the play, for example, his fellow Thebans referred to his bravery against the frightening Sphinx whom he alone outwitted and defeated.