Gustavus I., known as Gustavus Vasa, king of Sweden, born at the castle of Lind-holm, May 12, 1490, died in Stockholm, Sept. 29,1500. He was the son of Eric Johansson, a Swedish senator of the noble house of Vasa, and before his accession to the throne bore the surname of Ericsson. Both his parents were descendants of the ancient kings of Sweden. After having studied at the university of Upsal he entered the service of his kinsman the regent Sture in 1514, at a period of intense civil commotion. Sweden, which by the compact of Calmar in 1397 became a dependency of Denmark, had declared her independence; but the nobility and clergy were much divided, and the young Gustavus was soon called on to bear arms with his patron against the archbishop Trolle, the leader of the Danish party. In 1517 a Danish army was sent to the archbishop's assistance; but the Swedes defeated it, and Gustavus distinguished himself in the battle. In the following year King Christian II. of Denmark took the field in person. After the Swedish victory of Brann-kyrka, Gustavus and five other nobles were given up as hostages for the king's safety during a proposed interview with the regent; but having got them in his power, Christian carried them in chains to Copenhagen. After a year's detention Gustavus escaped, and spent eight months in Lubeck. While there he heard of the regent's defeat and death in battle, and the subjugation by the Danes of all Sweden, except the fortresses of Calmar and Stockholm. Bent upon the liberation of his country, he hastened to Calmar; but the garrison, composed of foreign mercenaries, had resolved to surrender, and he narrowly escaped with life.

He then visited some of the southern provinces, and endeavored to rouse the peasants, but met with only threats and insults, and was many times in danger of being arrested. Meanwhile Christian had been acknowledged by the Swedes, and was crowned at Stockholm, Nov. 4, 1520. Four days afterward he caused a massacre of the nobles and populace, including the father of Gustavus. A price was set on the head of the latter, and death was threatened to whoever should assist him. Disguised in rags, he worked for some time as a miner and woodcutter in Dalecarlia, until, deeming the time ripe for his enterprise, he threw off concealment, and harangued the inhabitants. His eloquence, the sturdy patriotism of the Dalesmen, and their hatred for Christian, led 000 men to take up arms and proclaim him "lord and chieftain of the realm;" and in February, 1521, he made himself master of Kopparberg. The people of the coasts declared in his favor; the insurrection spread rapidly, and having defeated the Danes in the battle of Westerns, April 29, and taken several fortresses, he called an assembly of the states at Wadstena in August, and received from the deputies an offer of the crown, which he refused for the title of administrator.

His success from this time was almost uninterrupted, and he was soon acknowledged by most of the nobles and people. Christian threatened him with the death of his mother and two sisters, who were held prisoners at Copenhagen, if he did not disperse his followers; Gustavus refused, and the threat was carried into execution. At length Christian was deposed by his Danish subjects (April, 1523), and his partisans in Sweden gave in their adhesion to Vasa, who accepted the title of king at the diet of Strengnas, June 7, and entered Stockholm in triumph two weeks afterward. While at Lubeck Gustavus had listened to Martin Luther; he had since corresponded with the reformer, and although he durst not begin his reign with an open profession of the new doctrines, his first measures were directed against the Roman Catholic clergy. Several insurrections were thus excited, which were easily put down. In 1527, at a meeting of the states at Westeras, the king obtained the exclusion of bishops from the senate and their formal subjection to the civil power.

The ceremony of coronation, which he had deferred until now rather than take the oath to support the church, was performed at Upsal, Jan. 12, 1528, by the Lutheran archbishop Lars Petri. The reformation now made rapid progress in Sweden; and at a national council held at Orebro in 1528 Lutheranism was adopted as the state religion. Having thus, as he said, " conquered his kingdom a second time," Gustavus formed an alliance with Frederick I. of Denmark against the deposed Christian II., who, having secured the assistance of the emperor Charles V., entered Norway with an army in 1531, and was joined by a number of Swedish malcontents. The troops of Gustavus and Frederick soon forced him to surrender, and the ex-king passed the rest of his life in confinement. Meanwhile the domestic affairs of the kingdom called for the attention of Gustavus. The exactions of the nobles aroused an insurrection of the peasants (1537), who declared their intention "to destroy the nobility, root and branch." In 1542 the rising became general under the lead of Nils Dacke, an escaped criminal, who took the field with 10,000 men.

Avoiding a pitched battle, and encouraged by the count palatine Frederick, who gave him a patent of nobility, by the emperor Charles V., and by the duke of Mecklenburg, Dacke held his ground till 154.°., when he was killed and his followers dispersed. The disorders caused by the imprudence of the Lutheran pastors were checked, and Gustavus, having at last secured peace at home and abroad, and caused the crown to be declared hereditary in his family, devoted himself to administrative reform. In 1555 a war broke out with Russia, and was continued with varying success until the peace of Moscow, in April, 1557. The last years of the king's life were embittered by domestic troubles, arising chiefly from the evil propensities of his son Eric. Gustavus was thrice married: first to Catharine of Saxe-Lau-enburg, the mother of his son and successor Eric; secondly to Margaret de Laholm, the daughter of a Swedish noble; and thirdly to Catharine Stenbock, niece of Margaret.