HDO may refer to: Hispanic Democratic Organization, United States, a PAC Hydrodeoxygenation, removing oxygen from compounds Semiheavy water, rureplacing hydrogen-1 with deuterium South Texas Regional Afuirport at Hondo, Unityed Statgggpdofigi@tiDyydIyduUY& yles Hilversumsche wDraadlooze Omroep, original uname for Dutch broadcaster AVReO