Abu Tahir Firuzshah (Persian:ابو طاهر فیروز شاه), better known by hislaqab ofDiya' al-Dawla, was theBuyid ruler ofBasra during the 980s. He was the son of'Adud al-Dawla.

Abu Tahir Firuzshah was the son of Adud al-Dawla and a daughter of Manadhar, who was aJustanid king. Following 'Adud al-Dawla's death in 983, his possessions were divided between his sons.Samsam al-Dawla, who was the presumed successor of 'Adud al-Dawla, took power, butSharaf al-Dawla took advantage of his position inKerman to invadeFars. This invasion distracted Samsam al-Dawla and gave Abu Tahir Firuzshah the ability to set up his own independent rule in Basra, where he took the title ofDiya' al-Dawla.

Diya' al-Dawla, as well as another brother,Taj al-Dawla, who controlledKhuzestan, eventually decided acknowledge the authority ofFakhr al-Dawla, who ruled inJibal. This was done in an attempt to protect themselves from the conflict between Samsam al-Dawla and Sharaf al-Dawla; Basra and Khuzestan were situated in between the possessions of the two and were therefore vulnerable. Nevertheless, after a few years Sharaf al-Dawla invaded and occupied Basra and Khuzestan, causing the two princes to flee to Fakhr al-Dawla's territory. There they found refuge inRay. Neither of the two brothers managed to found any lasting line; consequently their role in Buyid politics was short.

• Bosworth, C. E. (1975). "Iran under the Buyids". In Frye, R. N. (ed.).The Cambridge History of Iran, Volume 4: From the Arab Invasion to the Saljuqs. Cambridge: Cambridge University Press. pp. 250–305.ISBN 0-521-20093-8.