| Orseis | Orséis |
| Orselina | Orselina |
| Orsha | Orsha |
| Orsini | Famille Orsini |
| Orsini family | Famille Orsini |
| Orsières | Orsières |
| Orsk | Orsk |
| Orso I Participazio | Orso Ier Participazio |
| Orso II Participazio | Orso II Participazio |
| Orso Ipato | Orso Ipato |
| Orson Hodge | Orson Hodge |
| Orson Scott Card | Orson Scott Card |
| Orson Welles | Orson Welles |
| Ortac | Ortac |
| Ortaköy Mosque | Mosquée Ortaköy |
| Orteig Prize | Prix Orteig |
| Ortenaukreis | Ortenau |
| ORTF stereo technique | Office de radiodiffusion télévision française |
| Orthanc | Orthanc |
| Orthetrum | Orthetrum |
| Orthez | Orthez |
| Ortho-Nitrophenyl-β-galactoside | Ortho-nitrophenyl-β-galactoside |
| orthoclase | adulaire |
| orthodontics | orthodontie |
| orthodox | orthodoxe |
| Orthodox Church in Italy | Église orthodoxe en Italie |
| Orthodox Church of Constantinople | Église orthodoxe de Constantinople |
| Orthodox Judaism | Judaïsme orthodoxe |
| Orthodrome | Grand cercle |
| Orthogastropoda | Orthogastropoda |
| Orthogonal complement | Complément orthogonal |
| Orthogonal frequency-division multiplexing | Orthogonal Frequency Division Multiplexing |
| Orthogonal group | Groupe orthogonal |
| Orthogonal matrix | Matrice orthogonale |
| Orthogonal polynomials | Polynômes orthogonaux |
| orthographic | orthographique |
| orthography | orthographe |
| Orthohydrogen | Orthohydrogene |
| Orthomolecular medicine | Médecine orthomoléculaire |
| Orthomyxoviridae | Orthomyxoviridae |
| Orthonormal basis | Base de Hilbert |
| Orthonormality | Base orthonormale |
| Orthonychidae | Orthonychidae |
| orthopaedic | orthopédique |
| orthopaedics | orthopédie |
| orthopaedist | orthopédiste |
| Orthopantomogram | Orthopantomogramme |
| orthopedic | orthopédique |
| orthopedics | orthopédie |
| orthopedist | orthopédiste |
| Orthophoto | Orthophotographie |
| Orthopnoea | Orthopnée |
| Orthoptera | Orthoptera |
| orthopteran | orthoptère |
| Orthorexia nervosa | Orthorexie |
| Orthoscopic eyepiece | Oculaire orthoscopique |
| Orthosie | Orthosie |
| Orthosis | Orthèse |
| Orthrus | Orthos |
| Orto Botanico di Firenze | Jardin des simples de Florence |
| Orto botanico di Padova | Jardin botanique de Padoue |
| Orto botanico di Palermo | Jardin botanique de Palerme |
| Orto botanico di Pisa | Jardin botanique de Pise |
| Oruchuban Ebichu | Ebichu |
| Oruç Reis | Arudj Barberousse |
| Orval Brewery | Orval |
| Orvar Bergmark | Örvar Bergmark |
| Orvieto | Orvieto |
| Orville Wright | Frères Wright |
| Orvin | Orvin |
