| OROS Analytics | Oklahoma |
| Orosso | |
| Orostext, LLC | |
| Orourke | Massachusetts |
| ORPC, Inc. | |
| Orphai Therapeutics | |
| Orpheus, Inc. | District of Columbia |
| Orphic Workshop | New Mexico |
| Orphina Biotechnology | |
| Orphmedia, LLC | New York |
| Orpix, Inc. | |
| OrsoBio, Inc. | California |
| ORTEC | Georgia |
| OrthAlign | California |
| Ortho Development | |
| Ortho-tag, Inc. | |
| Orthobond Corporation | New Jersey |
| Orthofix Medical, Inc. | Texas |
| Orthoforge, Inc. | |
| OrthogenRx, Inc. | Georgia |
| Orthogon Therapeutics | |
| Orthogonal | Illinois |
| OrthoGrid Systems, Inc. | Utah |
| OrthoNovis, Inc. | |
| Orthopaedic Research of Virginia | Virginia |
| OrthoPediatrics Corporation | Indiana |
| Orthoscan, Inc. | Arizona |
| OrthoTrophix, Inc. | California |
| Ortiz Consulting | New Mexico |
| Ortus Books | Texas |
| Ortus Solutions Corporation | Texas |
| Orum, Inc. | |
| Oryan, LLC | |
| OS Therapies | |
| OS Ventures, Inc. | Florida |
| OS-Cubed, Inc. | New York |
| Osage University Partners | Pennsylvania |
| Osage Venture Partners | Pennsylvania |
| OSAM Document Solutions, Inc. | Pennsylvania |
| Osana | |
| Osano, Inc. | Texas |
| OSARO, Inc. | |
| Osborn Products, Inc. | Arizona |
| OSC Tech Lab | Ohio |
| OSC Web Design | Maine |
| OSCaM Technical | Virginia |
| Oscar Robotiques, Inc. | |
| Oscilar, Inc. | |
| Oscotec, Inc. | |
| OSCPS Motion Sensing, Inc. | |