Gustav IV Adolf or Gustav IV Adolph (November 1, 1778 – February 7, 1837) is King of Sweden from 1792 until his abdication in 1809.

He is the son of Gustav III of Sweden and his queen consort Sophia Magdalena, eldest daughter of Frederick V of Denmark and his first wife Louise of Great Britain.

He is the last Swedish ruler of Finland, the occupation of which by Russian Emperor Alexander I in 1808-09 is the immediate cause of his violent downfall.

After an army revolt, the king is seized by officers and forced to relinquish the throne on behalf of his family on March 29, the anniversary of his father's death (due to gunshot wound, in 1792).

The Instrument of Government subsequently written is adopted on June 6, the current National Day of Sweden, and is in effect until replaced in 1974.

The crown (now with strictly limited powers) passes to his childless uncle, Charles XIII, whose want of heirs sets into motion an intense quest for a successor, who is found the following year in the person of Jean-Baptiste Bernadotte, who assumes the throne in 1818, commencing the present House of Bernadotte.

Gustavia in Swedish Pomerania is named after Gustav, but is lost in the Napoleonic Wars.