GDI may stand for:
- Gasoline direct injection, a modern variant of fuel injection
- Gay Doctors Ireland, an independent grouping of LGBT medical professionals in Ireland
- Gender-related Development Index, an indication of the standard of living in a country, developed by the United Nations
- Global Defense Initiative, a fictional military organisation in the Command & Conquer computer game series
- Gonzaga Debate Institute, a popular summer policy debate workshop for high school students
- The Gottlieb Duttweiler Institute, a Swiss think-tank
- Graphics Device Interface, a core component of Microsoft Windows operating systems
- Gross domestic income, one of the National Income and Product Accounts
- Guanosine nucleotide dissociation inhibitors proteins in molecular biology
- Los Guerreros del Infierno, a Mexican professional wrestling stable
- God damn independent, a person not affiliated with a fraternity or sorority