CDU as a three-letter abbreviation can refer to:
- Cameroon Democratic Union, a political party in Cameroon
- Cash Dispenser Unit, which could be part of a Teller assist unit or an Automated teller machine
- Cebu Doctors' University, a medical university in the Philippines
- Centro Democrático Unido, a political party in El Salvador
- Charles Darwin University, a university in Darwin, Australia
- Christian Democratic Union (Germany), a German political party
- Christian Democratic Union (East Germany), a defunct political party
- Christian Democratic Union (Netherlands), a minor political party in the Netherlands between World War I and World War II
- Christian Democratic Union (Ukraine), a political party in Ukraine
- Cristiani Democratici Uniti, a former Italian political party
- Coolant Distribution Unit, used for water cooling in data centers
- Country Development Unit, a non-governmental organization in Afghanistan
- CentrumDemokraternes Ungdom, a youth organization in Denmark
- Clinical Decisions Unit
- Coligação Democrática Unitária, a leftist political coalition in Portugal
- Control Display Unit, a device used in remote operated gassfields
- Croatian Democratic Union, a conservative political party in Croatia led by Ivo Sanader
