1746–92, king of Sweden (1771–92), son and successor of Adolphus Frederick. When Gustavus ascended the throne, he found his kingdom torn by civil strife. To the conflicting interests of peasants, nobles, priests, and officials was added the struggle between the aggressive, pro-French, and aristocratic Hat party and the more conservative, pro-Russian Cap party. His efforts at conciliation having failed, the king placed himself in complete control by a coup. He imposed (1772) upon the estates a new constitution that restored to the sovereign the prerogatives lost by his predecessors. He immediately inaugurated a policy of rigid financial reform, made his fleet one of the most powerful in Europe, and proclaimed complete religious toleration. His extravagance and his emulation of the court of Versailles, however, offset many of his improvements. Because of the aggressive policy of Russian Empress Catherine II, Gustavus embarked (1788) upon a war with Russia, having first forced the rebellious Swedish gentry into promising their support. An officers' mutiny threatened the campaign with disaster, but when the Danes invaded Sweden at Catherine's instigation, the king rallied the lower classes and, with the moral support of Prussia and England, repulsed the attackers. In a second coup, Gustavus strengthened (1789) the regal authority. The following year he defeated the Russians, who then entered a defensive alliance with him. He was attempting to form a coalition to intervene in the French Revolution in favor of the royalists when he was assassinated at a masked ball by a representative of the nobles. He was succeeded by his son, Gustavus IV. A gifted and learned monarch, Gustavus was the author of dramas and poems. He patronized science and literature and founded (1786) the Swedish Academy.
- See Gustavus III and His Contemporaries, 1746–92 (1894). ,