HDO may refer to:

• Healthcare Delivery Organization
• Hispanic Democratic Organization
• Hydrodeoxygenation
• Semiheavy water
• South Texas Regional Airport at Hondo

• Dale D. Kelly
• Dale D Myers
• Dale D. Myers
• Dale Doig
• Dale Don Dale
• Dale Dubin
• Dale Duguid
• Dale Duward Brown
• Daleeae
• Dale Earnhardt Inc
• Dale Earnhardt, Sr
• Dale E. Christensen
• Dale Eggeling
• Dale Eldon Christensen
• Dale Eldred
• Dale End
• Dale End, Derbyshire
• Daleen Terblanche
• Dale Enterprise, Virginia
• Dale E. Saffels
• Dale E. Twomley
• Dale E. Wayrynen
• Dale Ferguson (designer)
• Dale Ferguson (rugby league)
• Dalefield railway station