Schloss Lannach, Renaissance castle in Lannach, Austria.

Schloss Lannach is a four-winged castle in the Kainachtal valley southwest of Graz, built from 1590 to 1610 for Christof von Galler. The complex is a protected monument and today houses the headquarters of G.L. Pharma, the company descended from the Lannacher Heilmittel GmbH founded in 1947.

From the 14th century the lords of Lannach held this site; in the first half of the 15th century it passed to the Galler family. Christof von Galler built the present four-winged castle between 1590 and 1610. A fire in 1714 caused major damage, and the building was soon restored. In the 19th century it belonged to the Freiherren von Mandell; in the 20th century Franz Kandler acquired it and founded a roof-tile and pottery factory there.

The name Lannach comes from the noble family of the same name, resident here from the 14th century; the Galler family followed in the first half of the 15th century. Since 1947 the site has housed the Lannacher Heilmittel GmbH, founded by Zirm and Loew, whose successor G.L. Pharma still has its headquarters in the castle. The Bartenstein family holds the majority shares.

Schloss Lannach is privately owned and not open to the public; it can be viewed from the outside. It lies in the Kainachtal valley southwest of Graz, not north of it. The building is a listed monument, so visitors should respect the private grounds.

During World War II, the SS used the castle as an institute for plant genetics while forcing nine Jehovah's Witness women into forced labor. This dark chapter is often overlooked but forms an important part of the site's complete historical record.