ʾAḥmad Ibn Yaḥyā al-BalādhurīArabic (أحمد بن يحيى بن جابر البلاذري) was a 9th-century Persian historian. One of the eminent middle-eastern historians of his age, he spent most of his life in Baghdad and enjoyed great influence at the court of the caliph al-Mutawakkil. He traveled in Syria and Iraq, compiling information for his major works. He is regarded as a reliable source for the history of the early Arabs and the history of Muslim expansion.
A Persian by birth, though his sympathies seem to have been strongly with the Arabs, for Masudi refers to one of his works in which he rejects Baladhuri's condemnation of non-Arab nationalism Shu'ubiyya.
He lived at the court of the caliphsal-Mutawakkil and Al-Musta'in and was tutor to the son of al-Mutazz. He died in 892 as the result of a drug called baladhur (hence his name). (Baladhur is Semecarpus anacardium, known as the "marking nut"; medieval Arabic and Jewish writers describe it as a memory-enhancer) 
His chief extant work, a condensation of a longer history, Kitab Futuh al-Buldan (فتوح البلدان), "Book of the Conquests of Lands", translated by Phillip Hitti (1916) and Francis Clark Murgotten (1924) in The Origins of the Islamic State, tells of the wars and conquests of the Arabs from the 7th century, and the terms made with the residents of the conquered territories. It covers the conquests of lands from Arabia west to Egypt, North Africa, and Spain and east to Iraq, Iran, and Sind.
His history, in turn, was much used by later writers. Ansab al-Ashraf (أنساب الأشراف, “Lineage of the Nobles”), also extant, is a biographical work in genealogical order devoted to the Arab aristocracy, from Muhammad and his contemporaries to the Umayyad and Abbāsid caliphs. It contains histories of the reigns of rulers.
His discussions of the rise and fall of powerful dynasties provide a political moral. His commentaries on methodology are sparse, other than assertions of accuracy.