Košťálov, Medieval castle ruin in Jenčice, Czech Republic.

Košťálov is a medieval castle ruin standing on a hilltop near Jenčice in the Czech Republic. The remains include stone walls and towers arranged to form defensive positions that controlled views of the surrounding landscape.

Košťálov is a donjon-type castle whose building form points to construction in the first half of the 14th century, although its first written mention dates from 1372; its builder and earliest owners are unknown. In 1422 a Hussite army camped below the castle, and by 1423 Jan Kaplíř probably held it. In 1486 three Kaplíř brothers divided the castle, and the family kept it until 1609, when Adam of Vchynice acquired it; by 1622 it was recorded as deserted.

The castle's name gave rise to the legend of its founding in the mid-8th century, invented by Václav Hájek z Libočan and published in his chronicle of 1541. The romantic setting drew Karel Hynek Mácha, who sketched the ruin twice in pencil around 1833, and Emil Filla, who painted it in the early 1950s in his series of lavírovaná tuš works on the České středohoří.

Marked trails lead to the ruin from Boreč (yellow trail, 2.5 km), Třebenice (red trail, about 3.3 km from the Třebenice město station), Sutom (asphalt road then yellow trail, 2 km) and Radostice (green trail, then cycle route 25). In every case the last 500 m from the trail junction is a forest path, in places quite steep. The upper palace masonry is unsecured and entry is not permitted.

The ruin has belonged to several private owners; the town of Třebenice tried to buy it but withdrew because of the high price. In 2024 the outer and lower castle were overgrown, and the upper palace masonry was losing architectural details. The Hrady Českého středohoří association surveyed the site.