The Hungarian National Seismological Network (HNSN) is a permanent seismological network operated by the Kövesligethy Radó Seismological Observatory (Geodetic and Geophysical Institute, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences). The main purpose of the network is the continuous monitoring of the seismicity of Hungary and to provide high quality data for the seismological and geodynamic scientific research. The first digital seismological station of the HNSN started its operation in 1992. The network covers the entire Hungarian territory although the geometry is driven by the topography. Most of the stations are concentrated in hilly/mountain regions to move away from the human related activities and to avoid basin effects. All data are acquired in real-time to the HNSN data centre located at the Kövesligethy Radó Seismological Observatory in Budapest. The HNSN follows an open data policy, seismic waveform data are available in real time without any restriction within from the HNSN data centre as well as from the European Integrated Data Archive via the GEOFON data centre.