HDI may refer to:
- Human Development Index, a United Nations measure of well-being in a country
- 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
- Heroux-Devtek Inc., a manufacturer of aircraft undercarriages
- Help Desk Institute, a professional organization for those working in the IT Service Management industry.
- High Density Interconnects, technology for complex electronic circuit designs in small form factor
- Hdi, an Afro-Asiatic language
HDi (formerly iHD) is Microsoft's implementation of the Advanced Content interactivity layer in HD DVD. It is used in the Xbox 360 HD DVD add-on as well as stand-alone HD DVD players.