historian important chiefly for his work in evaluating and publishing sources for Austrian history found in the Vienna state archives.

In 1841 Arneth was appointed by the Austrian statesman Klemens von Metternich to a post at the state archives, of which he became keeper in 1868. In 1879 he became president of the Imperial Academy of the Sciences, and in 1896 he was appointed chairman of the historical commission of the Bavarian Academy of the Sciences in Munich.

His chief publications concerned the 18th century and derived their value from the special facilities available to him. They include lives of Field Marshal Guido von Starhemberg (1853), Prince Eugene of Savoy (1858), and Maria Theresa (1863–79) and numerous collections of correspondence between Maria Theresa and Marie-Antoinette, Maria Theresa and Joseph II, Joseph II and Leopold, and Joseph II and Catherine of Russia. His early reminiscences, Aus meinem Leben, appeared in 1893.

Arneth had launched a political career as a member of the Frankfurt assembly in 1848, after which he served in the Lower Austrian Landtag (Diet) in 1861 and in the Herrenhaus (House of Lords) from 1869. He supported the liberal constitutional party.