| HPO | Hagemann Parent Organization 
| Others |
| HPO | Hamilton Philharmonic Orchestra
| Others |
| HPO | Handle Paper Once
| Others |
| HPO | Happy People Only
| Others |
| HPO | Head Post Office
| Others |
| HPO | Health Professions Office
| Others |
| HPO | Health Professions Organization
| Others |
| HPO | Health Promotion Office
| Others |
| HPO | Health Psychology Open
| Others |
| HPO | Healthcare Pricing Office
| Others |
| HPO | Herndon Plant Oakley
| Others |
| HPO | High Performance Oil
| Others |
| HPO | High Performance Optics
| Others |
| HPO | High Performance Optimisation
| Others |
| HPO | High Performance Option
| Others |
| HPO | High Performance Organisation
| Others |
| HPO | High Performance Organization
| Others |
| HPO | High Pressure Oil
| Others |
| HPO | High Priority Occupations
| Others |
| HPO | High Profile Object
| Others |
| HPO | High Volume Page Output
| Others |
| HPO | Highway Patrol Officer
| Others |
| HPO | Highway Post Office
| Others |
| HPO | Historic Preservation Office
| Others |
| HPO | History Projection Operator
| Others |
| HPO | Homeowner Protection Office
| Others |
| HPO | Hopkins Policies Online
| Others |
| HPO | Hopkins Policy Online
| Others |
| HPO | Hostalets de Pierola Observatory
| Others |
| HPO | Hrvatski paraolimpijski odbor
| Others |
| HPO | Hrvatskog paraolimpijskog odbora
| Others |
| HPO | Human Phenotype Ontology
| Others |
| HPO | Human Powered Ornithopter
| Others |
| HPO | Hungarian Patent Office
| Others |
| HPO | Hunter Point Online
| Others |