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. It is the biggest known Roman castellum in present-day Slovakia. It was a part of the Roman Limes, the frontier-zone of the Empire.