Frederick I, Swedish: Fredrik I, (17 April 1676 – 25 March 1751) is a prince consort of Sweden from 1718 to 1720, and a King of Sweden from 1720 until his death and (as Frederick I) also Landgrave of Hesse-Kassel from 1730.

He ascends to the throne following the death of his brother-in-law, absolutist Charles XII, in the Great Northern War, as his sister and heir Ulrika Eleonora prefers to abdicate from her position as queen regnant after relinquishing most powers to the Riksdag of Sweden.

His powerless reign sees his family's elimination from the line of succession after the parliamentary government dominated by pro-revanschist Hat Party politicians ventures into a war with Russia, which ends in defeat and the Russian Czaress demands Adolph Frederick of Holstein-Gottorp instated following the death of the king.