Celemantia (or Kelemantia; the modern name of the site is Leányvár) was a Roman castellum and settlement on the territory of the present-day municipality Iža (Hun: Izsa), some 4 km to the east of Komárno in Slovakia.
A Germanic settlement "Celemantia" in this area is mentioned by Claudius Ptolemaios in the 2nd century AD.
The fictitious story explains the origin of the name Leányvár, meaning Girl Castle in Hungarian.
However, the name probably refers to the fact that the ruins of the castle were donated by King Béla IV of Hungary to the Dominican nuns of Margitsziget who later built a small fortress among them.
In July 2021, Celemantia was added to the UNESCO's World Heritage List as part of the Western segment of the Danubian Limes of the Roman Empire.