Schloss Klessheim, Baroque castle in Wals-Siezenheim, Austria.

Schloss Klessheim is a Baroque castle in Wals-Siezenheim with a symmetrical facade and ornate decorative details. The building consists of several wings and features oval halls that structure its interior design.

Prince-Archbishop Johann Ernst von Thun bought the Kleshof estate in 1690 and commissioned Johann Bernhard Fischer von Erlach to build the palace from 1700. Work stopped at Thun's death in 1709 and was completed in 1732 under Leopold Anton von Firmian. From 1938 the Nazis used it for state receptions; the casino opened in 1993.

The palace's name recalls the Kleshof manor that stood here before 1700. Its garden was reshaped into an English landscape garden under Archbishop Hieronymus von Colloredo. From 1925 to 1935 Elizabeth Duncan, sister of Isadora Duncan, ran a dance school in the palace; Lucia Joyce, James Joyce's daughter, attended in 1928, and Joyce spent the 1928 festival season in Salzburg. Since 1993 the Salzburg casino has occupied the building.

The palace stands 4 km west of Salzburg's centre in Wals-Siezenheim, surrounded by a park with a golf course; the Tourismusschulen Salzburg sit below the terrace edge behind the building. Since 1993 the palace has housed the Salzburg casino, moved here from the Mönchsberg, so access follows casino opening hours rather than those of a museum.

The two entrance ramp pedestals carry reclining stags with golden stars on their antlers, carved by Josef Anton Pfaffinger in 1732 as a reference to the coat of arms of Archbishop Firmian. On the attic stands a marble coat of arms of Salzburg, Thun and Harrach, made by Bernhard Michael Mandl in 1707.