Abu'l-Husayn al-Qasim ibn Ubayd Allah (Arabic: أبو الحسين القاسم بن عبيد الله) was a senior official of the Abbasid Caliphate who served as vizier from April 901 until his own death in October 904.
Hailing from the Banu Wahb, a family of Nestorian Christian origin that had served in the caliphal bureaucracy since late Umayyad times, Ubayd Allah was the son and grandson of viziers.
[1] He had served as aide to his father, Ubayd Allah ibn Sulayman, during the latter's decade-long vizierate, and then succeeded him upon his death, heading the government during the last months of the reign of al-Mu'tadid (r. 892–902) and the early years of al-Muktafi (r. 902–908).
Al-Qasim largely dominated the young al-Muktafi, who awarded him with the title of Wali al-Dawla (Arabic: ولي الدولة, lit.
The powerful finance secretary Ali ibn al-Furat was saved from a similar fate only by al-Qasim's illness and death.