DDO

DDO may refer to:

Science and technology

 * David Dunlap Observatory Catalogue, a catalogue of dwarf galaxies that was published in 1959
 * DDO (gene), that encodes the D-aspartate oxidase enzyme
 * Distant detached objects, class of minor planets in the outer reaches of the Solar System
 * Dynamic Drive Overlay, a software technique to extend a system BIOS

Games

 * Dungeons & Dragons Online, a massively multiplayer online role-playing game

Titles

 * Deputy Director for Operations, particularly as the title of a specific CIA official; cf. article
 * The above title is sometimes incorrectly rendered as Deputy Director of Operations; especially this latter term is also in generic use as the title of officials in business or other organizations.
 * Director of Operations, particularly in francophone environments, from the French Directeur Des Opérations.
 * Diocesan Director of Ordinands, a priest in a Church of England diocese overseeing the ordination process

Other

 * DDO Artists Agency, a talent agency
 * Dollard-des-Ormeaux, on-island suburb of Montreal in southwestern Quebec, Canada
 * Tsez language, by ISO 639-3 code
 * Den Danske Ordbog, a dictionary of Danish
 * Davao de Oro