Abu Tahir Firuzshah (Persian: ابو طاهر فیروز شاه), better known by his laqab of Diya' al-Dawla, was the Buyid ruler of Basra 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 a Justanid 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, but Sharaf al-Dawla took advantage of his position in Kerman to invade Fars. 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 of Diya' al-Dawla.

Diya' al-Dawla, as well as another brother, Taj al-Dawla, who controlled Khuzestan, eventually decided acknowledge the authority of Fakhr al-Dawla, who ruled in Jibal. 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 in Ray. 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.

v t e Buyid dynasty
In Fars (934–1062)	Imad al-Dawla 'Adud al-Dawla Sharaf al-Dawla Samsam al-Dawla Baha al-Dawla Sultan al-Dawla Abu Kalijar Abu Mansur Fulad Sutun Abu Sa'd Khusrau Shah Abu Mansur Fulad Sutun
In Kerman (940–1048)	Mu'izz al-Dawla 'Adud al-Dawla Sharaf al-Dawla Samsam al-Dawla Baha al-Dawla Qawam al-Dawla Abu Kalijar
In Ray (943–1029)	Rukn al-Dawla Fakhr al-Dawla Mu'ayyad al-Dawla Fakhr al-Dawla Majd al-Dawla
In Iraq (945–1055)	Mu'izz al-Dawla Izz al-Dawla 'Adud al-Dawla Samsam al-Dawla Sharaf al-Dawla Baha al-Dawla Sultan al-Dawla Musharrif al-Dawla Jalal al-Dawla Abu Kalijar Al-Malik al-Rahim
In Oman (966–1048)	Mu'izz al-Dawla 'Adud al-Dawla Samsam al-Dawla Baha al-Dawla Sultan al-Dawla Abu Kalijar
In Hamadan (976–1024), Gorgan and Tabaristan (980–997)	Mu'ayyad al-Dawla Fakhr al-Dawla Shams al-Dawla Sama' al-Dawla
In Jazira (978-989)	'Adud al-Dawla Samsam al-Dawla Sharaf al-Dawla Baha al-Dawla
Minor domains	Diya al-Dawla (Basra, 980s) Taj al-Dawla (Khuzestan, 980s)