NSIS may refer to: Technology National Sheep Identification System, the implementation in Ireland for the identification and registration of ovine and caprine animals Network Store Interface Service, a Microsoft Windows service Next Steps in Signaling, a former Internet Engineering Task Force working group Nullsoft Scriptable Install System, a script-driven Windows installation system Other uses National Security Intelligence Section, of Ireland's Directorate of Military Intelligence New Sathorn International School, an international school located in Bangkok, Thailand