duke of Nassau from 1839 to 1867, who, as grand duke of Luxembourg from 1890 to 1905, was the first ruler of that autonomous duchy.

The son of Duke William of Nassau-Weilburg and Charlotte of Saxony, Adolf became duke of Nassau upon his father's death (1839). Educated in Vienna and a military supporter of the Habsburgs, he sided with Austria against Prussia in the Seven Weeks' War (over hegemony in German affairs); and, upon the defeat of Austria (1866), Nassau was annexed by Prussia. He formally abdicated as duke of Nassau (Sept. 9, 1867) and was granted 8,500,000 thalers and a few castles as compensation. He served as regent of Luxembourg for King William III of The Netherlands in 1889; when the male line of Orange-Nassau ended with William III's death (1890) and the personal union between Luxembourg and The Netherlands ceased, the grand duchy reverted, according to the 1783 Nassau Succession Agreement, to him as the head of the ducal house of Nassau-Weilburg. Ruling until his death, he was succeeded by his son, Grand Duke William IV.

Adolf, who was count of Nassau from 1277 and a mercenary soldier of repute, was chosen king at Frankfurt by the German electors, who preferred him to Albert as successor to Albert's father, Rudolf I, the first Habsburg king. After his coronation at Aachen on June 24, 1292, Adolf had to face exorbitant demands by his electors and the hostility of Albert, who as duke of Austria commanded great financial and territorial resources.

Adolf seized Meissen as a vacant fief and purchased the right of succession in Thuringia from the landgrave Albert. His alliance with King Edward I of England against France (Aug. 24, 1294) brought him a cash subsidy, which he spent in defeating the landgrave's disinherited sons, Frederick the Dauntless and Dietzmann (Dietrich). The German electors, alarmed by Adolf's growing power, decided to transfer the crown to Albert, with whom they had been negotiating. Albert's large army was present at Mainz when the sentence of deposition was pronounced. Adolf attempted to regain the throne in battle against his rival's superior forces but was defeated and killed.