| Acronym | Definition |
|---|
| ONB | Orthonormal Basis (mathematics) |
| ONB | Old National Bancorp |
| ONB | Opera Nazionale Balilla (Italian: National Opera Balilla; youth organization) |
| ONB | On Board (philately; Zeppelin mail designation) |
| ONB | Operation New Birmingham (Alabama) |
| ONB | One Night Band |
| ONB | Oesterreichische Nationalbank (Austria) |
| ONB | Optimal Normal Basis |
| ONB | Ordine Nazionale Dei Biologi (Italian: National Order of Biologists) |
| ONB | Onset of Nucleate Boiling |
| ONB | Opéra National de Bordeaux (French: Bordeaux National Opera; Bordeaux, France) |
| ONB | Ocala National Bank (Florida) |
| ONB | Order of New Brunswick |
| ONB | Occipital Nerve Block |
| ONB | Orienteering New Brunswick |
| ONB | On Blocks (aircraft arrived at parking position) |
| ONB | Oren Nayar Blinn (form of shading used in 3D graphics) |
| ONB | Ocean Networks Branch |
| ONB | Our Neighbor Barry (band) |
| ONB | Overnight Bin |