Gustavus III., king of Sweden from 1771 to 1792; succeeded his father Adolphus Frederick; he found himself early at conflict with his nobles, and in 1772, supported by popular feeling, imposed a new constitution on the country greatly diminishing their power; Gustavus was an enlightened ruler, but somewhat alienated his people from him by his extravagance and fondness for French modes of life; in 1788 he became embroiled in a purposeless war with Russia; he was assassinated when about to take up arms in behalf of the Bourbon cause against the French Republicans (1746‒1792).
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Gustavus (II.) Adolphus * Gustavus IV.