Ozai was the Fire Lord and absolute ruler of the Fire Nation during the final years of the Hundred Year War. He was the second son of Azulon and Ilah, the younger brother of Iroh, uncle of Lu Ten, husband to Ursa, the father of Prince Zuko and Princess Azula, and grandfather to Izumi. Ozai was a firebending master and, prior to the ending of the War, was believed to have been one of the most powerful firebenders in the world.

After Iroh's only son, Lu Ten, died, Ozai usurped his brother's birthright to the throne in a scheme that resulted in his father's death and Ursa's banishment.