ESI or Esi may refer to:
Science and technology Earth Similarity Index Electrospray ionization, a technique used in mass spectrometry Environmental Seismic Intensity scale Essential Science Indicators, by Clarivate Electronic supplementary information, in scientific publications; for example see coordination polymerization
Computing Edge Side Includes, a markup language Electronically stored information (Federal Rules of Civil Procedure) Enterprise Southbridge Interface, a motherboard interface ESI register, in the x86 microprocessor architecture
Medicine Electromagnetic source imaging Emergency Severity Index, a triage algorithm Epidural steroid injection
Organisations Electro Scientific Industries, an American high-technology company Employees' State Insurance, in India ESI Hospital metro station, Delhi ESI Hospital metro station (Hyderabad) Ernst Strüngmann Institute, a German research institute Erwin Schrödinger International Institute for Mathematical Physics, in Austria Escadron spécial d'intervention, now the Belgian Federal Police Special Units European Stability Initiative, a think tank ITT Educational Services, owner of the defunct ITT Technical Institute
People Esi Awuah, Ghanaian academic Esi Benyarku (born 1976), Canadian sprinter Esi Buobasa, Ghanaian activist Esi Edugyan (born 1978), Canadian novelist Esi Lufo (born 2001), Albanian footballer Esi Sutherland-Addy, Ghanaian academic Esikeli Tonga (born 1988), Australian rugby league player
Other uses Enhanced Station Initiative, of the New York City Subway Enlightened self-interest, a philosophy in ethics Environmental Sustainability Index Ethical Sensory Introvert, in socionics Export substitution industrialization Early supplier involvement, an aspect of supplier integration in new product development North Alaskan Inupiatun language (ISO 639-3 code)