Častkov is a village and municipality in Senica District in the Trnava Region of western Slovakia.
In historical records the village was first mentioned in 1394.
The municipality lies at an altitude of 280 metres and covers an area of 13.182 km². It has a population of about 610 people.
The records for genealogical research are available at the state archive "Statny Archiv in Bratislava, Slovakia"
- Roman Catholic church records (births/marriages/deaths): 1697-1910 (parish B)
- Lutheran church records (births/marriages/deaths): 1733-1902 (parish A)
Coordinates: 48°45′N 17°21′E / 48.750°N 17.350°E