Levnov, Castle ruin in Ketkovice, Czech Republic.

Levnov is a castle ruin on a rocky promontory 120 metres above the Oslava and Chvojnice rivers, near their confluence. Below the castle rock stands the Ketkovický mill. The site lies in the Oslava and Chvojnice Valley nature reserve, three kilometres south of Ketkovice.

Levnov was built at the start of Charles IV's reign by Léva of Levnov, whose family died out around 1400. In the 15th century it passed to the Lords of Lipá of Moravský Krumlov, and after the Hussite Wars German mercenaries under Burghart Kienberger seized it. Bought back by Brno, Znojmo, Ivančice, Třebíč and Jihlava, it was demolished in November 1442 under the 1440 Znojmo resolution against robber castles.

The name Levnov was only restored to the ruin in 1970, when archival records identified the site; before then its location was unknown. The castle took its name from Léva of Levnov, who built it at the start of Charles IV's reign. The Lords of Lipá held it in the 15th century.

The ruin stands on a 120-metre rock spur above the Oslava and Chvojnice, on a marked trail 3 km south of Ketkovice, inside the Údolí Oslavy a Chvojnice reserve. The Ketkovický mlýn lies directly below the castle rock. The site is unprotected rock terrain, so sturdy footwear matters.

The ruin only regained the name Levnov in 1970, when archival records identified the site; before then its location was unknown. It was demolished in November 1442 by order of the Moravian estates, and the surrounding villagers who helped could take the building stone away.