Gråsten (Danish pronunciation: [kʁɔˈste̝ˀn]; German: Gravenstein) is a town with a population of 4,336 (1 January 2024) on the east coast of the Jutland peninsula in south Denmark by the Nybøl Nor at an inlet of the Flensburg Fjord. It belongs to the Sønderborg municipality in Region of Southern Denmark. The town is located almost exactly at the center of a triangle defined by the towns of Aabenraa, Flensburg and Sønderborg Castle (Sønderborg Slot).

The Egernsund Bridge, which crosses the Egern Strait, connects Gråsten with the town of Egernsund. Gråsten is served by Gråsten railway station, located on the Sønderborg railway line.

The Gravenstein apple originates from the town.

Until 1 January 2007 Gråsten was the seat of the former Gråsten municipality (Danish, kommune) in South Jutland County, covering an area of 57 km, and with a total population of 7,256 (2005). Its last mayor was Bendt Olesen, a member of the Social Democrats (Socialdemokraterne) political party. The municipality was created in 1970 due to a kommunalreform ("Municipality Reform") that combined the following parishes: Gråsten, Kværs, Rinkenæs, and Adsbøl.

Gråsten municipality ceased to exist due to Kommunalreformen ("The Municipality Reform" of 2007). It was combined with Augustenborg, Broager, Nordborg, Sundeved, Sydals, and Sønderborg municipalities to form the new Sønderborg municipality. This created a municipality with an area of 499 km and a total population of 49,886 (2005).

The Danish royal family has their summer residence, Gråsten Palace, in the town

• Andreas Hohwü (1803–1885), a Danish clockmaker active in Amsterdam
• Adolf Ditlev Jørgensen (1840–1897), Danish historian and archivist
• Margarete Mitscherlich-Nielsen (1917–2012), German psychoanalyst
• Anne Wolden-Ræthinge (1929–2016), Danish journalist, known by the pseudonym Ninka

• The new Sønderborg municipality's official website Archived 2015-10-02 at the Wayback Machine (in Danish)
• Gråsten Palace (in Danish)

• Municipal statistics: NetBorger Kommunefakta, delivered from KMD aka Kommunedata (Municipal Data)
• Municipal mergers and neighbors: Eniro new municipalities map