| ORACION 0809508 · TMA511181 · design | Hands On Entertainment Inc. | 9 Electronics | Registered | 1999 |
| ORAGON 1801142 · TMA1045638 | mixi, Inc. | 9 Electronics28 Toys41 Education | Registered | 2019 |
| ORCON 1278610 · TMA687963 · design | Biologische Insel Lothar Moll GmbH & Co. KG | 1 Chemicals8 Hand17 Rubber | Registered | 2007 |
| ORGANON 2005451 · TMA1184663 | an individual | 5 Pharmaceuticals9 Electronics10 Medical+2 | Registered | 2023 |
| ORGANON 0823349 · TMA510252 · design | an individual | 5 Pharmaceuticals | Registered | 1999 |
| ORGANON 0153318 · TMDA51273 | an individual | 1 Chemicals | Registered | 1931 |
| ORACING 2061170 · design | Sunrise Medical (US) LLC | 12 Vehicles28 Toys35 Advertising | Pending | 2020 |
| ORAGEN 2215717 · TMA1238958 | an individual | 5 Pharmaceuticals | Registered | 2024 |
| ORIZON 2114585 · TMA1205018 · design | an individual | 5 Pharmaceuticals9 Electronics10 Medical | Registered | 2023 |
| ORIZON 2101581 · TMA1204975 | an individual | 5 Pharmaceuticals9 Electronics10 Medical | Registered | 2023 |
| ORIZON 2088415 · TMA1186050 | an individual | 25 Clothing | Registered | 2023 |
| ORIZON 2019941 · TMA1283816 | Saudi Arabian Oil Company | 1 Chemicals4 Oils42 Science | Registered | 2025 |
| ORIZON 1941882 · TMA1172943 | an individual | 35 Advertising42 Science | Registered | 2023 |
| ORCAN 1893775 · TMA1102312 | an individual | 7 Machines9 Electronics11 Lighting+1 | Registered | 2021 |
| OREGON 1532655 · TMA912284 | Oregon Tool, Inc. | 7 Machines | Registered | 2015 |
| ORIKON 1520014 · TMA823175 | MÉDICAL TRONIK MTL LTÉE | 10 Medical | Registered | 2012 |
| OREGON 1466319 · TMA855685 · design | Oregon Tool, Inc. | 7 Machines | Registered | 2013 |
| OREGON 1154116 · TMA644155 · design | Oregon Tool, Inc. | 7 Machines12 Vehicles | Registered | 2005 |
| ORCOM 0859843 · TMA527815 | Orcom Solutions, LLC | 9 Electronics16 Paper42 Science | Registered | 2000 |
| OREGON 0789369 · TMA472365 | Global Contract Limited Partnership (an Ontario limited partnership) | 20 Furniture | Registered | 1997 |
| OREGON 0230646 · TMA103080 | Oregon Tool, Inc. | 7 Machines8 Hand9 Electronics | Registered | 1956 |
| OREGON 2039198 · design | Oregon Tool, Inc. | 4 Oils7 Machines8 Hand+1 | Pending | 2020 |
| OREGON 2039195 | Oregon Tool, Inc. | 4 Oils7 Machines8 Hand+1 | Pending | 2020 |
| OREGON 1999727 · design | Oregon Tool, Inc. | 7 Machines | Pending | 2019 |
| OREGON 1999726 | Oregon Tool, Inc. | 7 Machines | Pending | 2019 |