HDI may refer to:
- Human Development Index, a United Nations measure of well-being in a country
- Human Development Initiatives, an NGO in Nigeria
- PSA HDi engine, a diesel automobile engine by Peugeot/Citroën
- Hexamethylene diisocyanate, an organic compound used to make polymers such as polyurethane
- HDi Interactive Format (formerly iHD), a trademark for Microsoft's implementation of advanced interactivity for HD DVD
- Histone deacetylase inhibitor, compounds used in psychiatry and neurology, and with anticancer potential
- HDI-45 connector, a video connector by Apple