| Odenti | Vienne |
| Odimma Therapeutics | |
| Odit-e | |
| Odity | |
| ODW S.A.S. | |
| Odyssée Conseil | |
| Odyssée Informatique | Corrèze |
| Odyssee Software | Loire |
| Odyssée Venture | Paris |
| Odyssey Messaging | Paris |
| OECD.AI | |
| OELIS | Loire |
| OEM Horanet | Vendée |
| Off-Works | |
| OFF7, l'accélérateur du Groupe Ouest-France | |
| Office Formation | Haute-Garonne |
| OfficeEasy S.A.S.U. | Nord |
| OfficePartner | Haut-Rhin |
| OfficeXpress | Seine-Saint-Denis |
| OFIS Informatique | Métropole de Lyon |
| OGI | Aveyron |
| Ohayo | Nord |
| OHM Games | |
| Ohm Studio S.A.R.L. | Paris |
| oHRIS | Nord |
| OHweb | Haute-Garonne |
| Okeiro | |
| OKINA | |
| Oklin | Yvelines |
| Okomera | |
| OKTEO | |
| OKTEY | Haute-Garonne |
| Oktos | |
| Old Skull Games | |
| Olea Medical S.A.S. | |
| oledcomm S.A.S. | Yvelines |
| Olfeo | Paris |
| Olivgraphic | Métropole de Lyon |
| Ollivier | |
| OLRAS | Meurthe-et-Moselle |
| Olynsoft | |
| OM Conseil | Yvelines |
| Ombrea | |
| OMEGA Informatique S.A.R.L. | Alpes-Maritimes |
| Omerin S.A.S. | Puy-de-Dôme |
| Omi | |
| Omicron | Hérault |
| Omnes Capital | |
| OMNES Education | Paris |
| Omniciel | Bouches-du-Rhône |