Adolphus Frederick, of Holstein-Eutin, king of Sweden, born May 14, 1710, died Feb. 12,1771. In 1727 he was elected prince-bishop of Lubeck as successor of his father. On the death of his cousin Charles Frederick, duke of Holstein-Gottorp, in 1739, Adolphus Frederick became the administrator of his possessions during the minority of his son, afterward Peter III. of Russia. The king of Sweden, Frederick of the house of Hesse-Cassel, being childless, and the young duke of Holstein-Gottorp having declined to become heir apparent at a time when he hoped to succeed to the throne of Russia, it was decided in 1743, by virtue of the treaty of Abo between Russia and Sweden, that Adolphus Frederick should occupy the position, so that it might be at all events vested in the Holstein family. The grandmother of Adolphus having been a daughter of Charles XI. of Sweden, this circumstance was also regarded as favorable to his election, which was ratified by the Swedish diet on July 3, 1743. In 1744 he married Louise Ulrike, a sister of Frederick the Great, and he ascended the Swedish throne April 5, 1751, on the death of King Frederick. The aristocracy being favorable to France, Sweden was dragged into the seven years' war against Prussia; and the attempts of the queen to oppose this policy resulted only in bringing the ringleaders against the aristocracy to the scaffold (1756). The council of state sided with the aristocracy against the crown, and it was only after the king's threatening to abdicate that the Swedish diet consented to sustain his rights and protect him against the aggressions of the nobles.

He was an upright prince, but by his meekness ho encouraged the schemes of France and her allies among the nobility. He was succeeded on the throne by his son Gustavus III.