FDD may refer to:
- Floppy disk drive
- Foundation for Defense of Democracies, a policy institute based in Washington, DC.
- Feature Driven Development, a project management approach
- National Council for the Defense of Democracy-Forces for the Defense of Democracy, a rebel group in Burundi
- Frequency-division duplexing, a telecommunications duplex indexing method
- Franchise Disclosure Document (2008) UFDD/UFOC Uniform Franchise Offering Circular
- Former District Deputy when used after the name of a member of the Knights of Columbus
- Focus-to-detector distance, a distance between the focus of an x-ray tube and detector in dosimetry
- Frequency domain decomposition, a system identification technique
- Francoise Danielle Decatrel