Sibawayh was a linguist of Persian origin writing in Arabic who wrote the first great grammar of Arabic. He worked mostly in Bagdad, but died in Shiraz around the year 180/796.
His full name was 'Amr ibn 'Uthman ibn Qanbar. Sibawayh is a nickname.
Sibawayh was a non-Arab writing on Arabic grammar and he explained Arabic grammar from a non-Arab perspective. He was probably not a native speaker of Arabic.