DDI can be an abbreviation for:
- D&D Insider, an online method used to deliver Dungeons & Dragons content.
- Dance Dance Immolation, a spin-off of Dance Dance Revolution involving flamethrowers
- Dartmouth Debate Institute, a summer program run by the Dartmouth Forensics Union
- Data Design Interactive, an infamous UK video game developer.
- Data Documentation Initiative, a Metadata standard for statistical data.
- Device Driver Interface, a low-level driver application programming interface
- Didanosine, an antiretroviral drug
- Direct Dial-In, another name for Direct Inward Dialing
- Diverging diamond interchange
- Divisional Detective Inspector
- DNS DHCP IPAM, commonly referred simply as IPAM
- Drug-drug interaction.