Casimirsborg, Empire-style château in Västervik Municipality, Sweden

Casimirsborg is a three-storey Empire-style manor with two matching wings, built in 1829 on the shores of Gamlebyviken. Its cellars date from the 14th century and retain a dungeon from the first castle on the site. The estate today comprises 13 houses, farmland and forestry.

The estate received manor privileges around 1618 when Count Johan Casimir Lewenhaupt acquired and unified several farms in the medieval area of Mæm. This elevated the land from farmland to a noble residence.

The chapel, completed in 1829, is one of Sweden's earliest Gothic revival interiors and was inspired by the Gothic Room at the Royal Palace in Stockholm. Its walls are decorated with trompe-l'œil painting, and the room has remained unaltered since its completion. The chapel adjoins the Grand Salon and can be seen on private tours.

The house is not generally open to the public; private tours and occasional function hire are possible by prior arrangement. The estate today comprises 13 houses, farmland and forestry, so visitors stay on the grounds and paths rather than entering the residence unannounced.

The grand reception hall stands as one of the largest private spaces of its kind in the region, demonstrating the scale at which the nobility entertained. The room once hosted important social gatherings and celebrations on the estate.