The purpose of the research was to study major hydrological droughts in Slovakia in the 21st century. Drought origin, severity, spatial distribution, impacts on the ecosystems and society and implemented measures were analyzed. Drought is a singular natural hazard, difficult to be recognized in its initial phase, specific with slow onset, possible long duration, with non-structural, multi-facetted impacts, globally affecting more regions and more peoples than other natural hazards. Slovakia was hit by several severe droughts in the 20th century (1927, 1947-1948, 1982-1983 and (1992-1993) and by three major droughts in 2003, 2012 and 2015 in the 21st century. Daily discharges at 12 gauging profiles of main river basins, weekly groundwater level and spring yield data at 116 groundwater monitoring network objects were used as the basic data for hydrological drought studies. Global climatic situation and regional conditions were taken into account by initial conditions description. Method of SPA with the fixed threshold of the 80th percentile of the long-term flow duration curve was used for hydrological drought periods estimation. Three-parametric Weibull distribution and generalized extreme values distribution were used to calculate return period of drought in four basic drought parameters - minimum value expressed as AM7, drought duration, maximum deficit volume and drought intensity. Timing of drought and its seasonality were also studied. Groundwater drought in groundwater levels and spring yields was analyzed using the SANDRE method developed by French Data Reference Centre for Water. The results showed that the initial climatic conditions over the Europe were quite similar in all three years. There was a positive 500-hPa geopotential height anomaly in the upper level atmospheric circulation over the continental Europe, especially over the central and Eastern Europe. The temperature in summer and beginning of fall in Slovakia in all three years was higher, but the precipitation totals were lower than the long-term average of 1960-1990. Comparison of calculated hydrological drought parameters showed that the 2015 drought was the severest of all studied droughts. The impacts were manifold across the country. The ecological impacts included deterioration of the oxygen regime in surface streams, drying up of small surface streams and springs, decrease of groundwater levels and occurrence of wild fires. Vegetation stress resulted in lower hay harvest, failing grass cut and crop losses of 50 %. Drying of springs and decrease of groundwater levels resulted in shortage in drinking water-supply for inhabitants. There was a dramatically increased number of collapsing people because of extreme heat. The measures taken included backwater at small streams in order to increase the oxygen content, replacement of rock lobsters and fishes, restrictions of drinking water use, but also street sprinkling, availability of drinking water in water tanks and arrangement of sprinkling fountains for people in the streets, lowering of admission charges and prolongation of opening hours for public swimming pools, increase of number of air-conditioned wagons in railway public transportation or abridgment of working hours. As a conclusion, proposal of further drought research orientation and required policy measures were delineated.