| Oregon State University Department of Mathematics | Oregon |
| Oregon State University School of Electrical Engineering and Computer Science | Oregon |
| Oregon Venture Fund | |
| Oregon Web Solutions | |
| Oregon's Best Internet Services, Inc. | Oregon |
| OregonWebsiteDesign.com | Oregon |
| Oréll, Inc. | Colorado |
| Orentreich Foundation for the Advancement of Science | |
| Orfium | California |
| OrganaBio | Florida |
| Organic Design | |
| Organic Mindset Agency | |
| Organical | |
| Organicell Regenerative Medicine, Inc. | Florida |
| Organix | Massachusetts |
| Organizer, Inc. | California |
| Organizlen Global Digital Marketing Solutions | New York |
| Organogenesis, Inc. | Massachusetts |
| Organon Group of Companies | |
| Organovo Holdings, Inc. | California |
| OrgChart by OfficeWork Software | California |
| Orgenesis, Inc. | Maryland |
| Orgnet, LLC | Ohio |
| OrgPlus | California |
| Ori Design Studio | |
| ORI.NET | Indiana |
| ORIC Pharmaceuticals, Inc. | |
| Orienge, LLC | |
| Orientier, Inc. | |
| Origami | |
| Origami Risk | Illinois |
| Origami Studios | New Jersey |
| Origami Surgical, LLC | New Jersey |
| Origami Therapeutics, Inc. | |
| OriGen Biomedical | Texas |
| OriGene Technologies, Inc. | Maryland |
| Origent Data Sciences, Inc. | District of Columbia |
| Origin Partners | New Jersey |
| Origin Protocol, Inc. | |
| Origin Ventures | Illinois |
| Origin Wireless, Inc. | Maryland |
| Origin, Inc. | New Jersey |
| Original Account Strategies, LLC | |
| Original Wannabe, LLC | |
| Originate, Inc. | California |
| OriginClear | |
| ORIGINET, Inc. | New York |
| OriginLab | Massachusetts |
| Origyn, Inc. | |
| Orijin | |