Inu no Taishou (犬の大将, Inu no Taishō?) is a fictional character from the anime and manga series, InuYasha. He was a great and powerful yōkai lord who was known throughout Japan. He fathered Sesshomaru with another dog yōkai (Sesshomaru's Mother), and InuYasha with a human woman, Izayoi. While he is often known as Inutaisho by fans, the yōkai lord has no official name. "Inu no Taishou" is merely the Japanese term for his title of "Dog General". He is also known as "The Great Dog Demon", which is a translation of the term used in the English version of the series.

Despite never appearing outright (except in the intro of the third movie), his will has been one of the most influential driving forces in the series. Possessing forethought bordering on clairvoyance, much of his sons' acquisition of power has come as a direct result of trials he set in place before his death. Yet despite having so much influence, very little is known about him.

Source: Wikipedia