Kotnov, Medieval castle ruins in Tábor, Czech Republic.

Kotnov is a medieval castle ruin whose main features are a round tower and the adjacent Bechyně Gate, both standing out on Tábor's skyline. These remains are from a 13th-century fortification complex that once protected the city.

Kotnov was founded by King Přemysl Otakar II in the third quarter of the 13th century as a royal castle called Hradiště, first mentioned in writing in 1370. After 1420 it was rebuilt by the Hussites and incorporated into Tábor's fortifications. A fire in 1532 left it ruined; from 1612–1613 most buildings were converted into a brewery, and in 1908 the east wing was rebuilt for industry, leaving only the tower.

The permanent exhibition in the Gothic rooms of the Bechyně Gate is titled "Life and Occupations of Medieval Society". The gate itself was begun in 1420 as part of the Hussite fortification of Tábor and was rebuilt in High Gothic style under Josef Mocker at the end of the 19th century.

Visitors can climb the round tower to reach viewing platforms that offer wide views across Tábor and the Lužnice river valley. The site is accessible on foot with paths leading directly to the tower's base and the gate.

The round battery tower is 25 metres high and now holds a viewing platform run by the Hussite Museum in Tábor. Its lower storey reuses the masonry of an older tower, and the two building phases remain visible in the wall. The parapet of the gallery has keyhole loopholes fitted with wooden beams to support handguns.