Abu Nasr Khusrau Firuz (died 1058 or 1059) was the Buyid amir of Iraq (October 1048-1055). He was the son of Abu Kalijar.
Upon his father's death, he took the throne in Baghdad with the title "al-Malik al-Rahim". His succession to the entire Buyid Empire was prevented by his brother Abu Mansur Fulad Sutun, who took control of Fars. The two then entered into a struggle for supremacy. al-Malik al-Rahim took Shiraz, but was then forced back to Iraq due to increased hostility between the Turks and the Dailam troops there. At about the same time, the Buyid lands in Oman were permanently lost. In 1051 or 1052, however, he defeated Abu Mansur and captured Fars. al-Malik al-Rahim then appointed another brother, Abu Sa'd Khusrau Shah, as governor of the province. Shiraz, however was lost in 1053 or 1054, when Abu Mansur returned as a vassal to the Seljuk ruler Toghrül.
Toghrül soon decided to put an end to the Buyid state in Iraq. On December 17, 1055, he arrived in Baghdad as a pilgrim on his way to Mecca, and made it known that after he returned, he would make war with the Fatimids. The caliph, who had initially preferred the weak Buyids over the strong Seljuks despite the latter's Sunni orthodoxy, declared that Toghrül's name should be recited before the al-Malik al-Rahim in the Friday sermons. The amir thereupon became a vassal of the Seljuks.
Barely a week had passed, however, before the citizens of Baghdad began to complain to the amir about looting committed by the Seljuk troops, asking him to expel them out of the city. Toghrül then summoned him to his camp to negotiate over the issue. When he arrived, he was accused of acts of retribution against the Seljuk troops, and was arrested over the caliph's protests. al-Malik al-Rahim was the last Buyid ruler of Iraq. He died a prisoner in Ray in 1058 or 1059.