| OMYASPACE 1506306 · TMA822337 | an individual | 1 Chemicals | Registered | 2012 |
| OneSpace 1692238 · TMA979051 | an individual | 6 Metal9 Electronics11 Lighting+2 | Registered | 2017 |
| ONESPACE 2346300 | Rightworks, LLC | 42 Science | Pending | 2024 |
| OWNSPACE 2299579 | Owner not listed | 9 Electronics35 Advertising42 Science | Pending | 2023 |
| OWNSPACE 2299576 · design | OwnSpace Solutions Inc. | 9 Electronics35 Advertising42 Science | Pending | 2023 |
| OMNISPAN 1455750 · TMA837712 | Owner not shown | 10 Medical | Registered | 2012 |
| OMNISPARK 2330113 | Owner not listed | 7 Machines | Pending | 2024 |
| OMNISCAPE 2293592 | an individual | 11 Lighting | Pending | 2023 |
| oncoflake 2183708 · TMA1229630 | Oncoradiomics | 9 Electronics42 Science44 Medical | Registered | 2024 |
| OMNISHOP 2169237 · TMA1282577 | Cloud Drop Technologies LLC | 9 Electronics14 Jewellery16 Paper+7 | Registered | 2025 |
| ONCOBIX 2146652 · TMA1228857 · design | ONCOBIX CO., LTD. | 5 Pharmaceuticals | Registered | 2024 |
| ONESHOP 2144537 · TMA1201685 · design | Inventory Systems Inc. | 42 Science45 Legal | Registered | 2023 |
| ONESPORT 2119011 · TMA1186396 · design | Dongguan onesport Technology Co. Ltd | 12 Vehicles | Registered | 2023 |
| ONCOPREX 2089152 · TMA1214024 | Genprex, Inc. | 5 Pharmaceuticals | Registered | 2023 |
| OMGEVI 2089065 · TMA1196487 | Theravance Biopharma Ireland Limited | 5 Pharmaceuticals | Registered | 2023 |
| OMNISPEND 2081260 · TMA1150613 | Market Track, LLC | 9 Electronics35 Advertising42 Science | Registered | 2022 |
| OMNICEPT 2060646 · TMA1278414 | Hewlett-Packard Development Company, L.P. | 9 Electronics | Registered | 2024 |
| ONECABLE 2036998 · TMA1270704 | an individual | 9 Electronics | Registered | 2024 |
| ONECABLE 2036997 · TMA1270703 · design | an individual | 9 Electronics | Registered | 2024 |
| ONCOPEPTIDES 2033388 · TMA1227653 | an individual | 1 Chemicals5 Pharmaceuticals42 Science | Registered | 2024 |
| OmegaPower 2001204 · TMA1271975 | OCEANBLUE LLC | 5 Pharmaceuticals | Registered | 2024 |
| OncoFreeze 1942178 · TMA1159644 | Siemens Medical Solutions USA, Inc. | 9 Electronics | Registered | 2023 |
| ONCOVANT 1939566 · TMA1125507 | Roivant Sciences GmbH | 5 Pharmaceuticals42 Science44 Medical | Registered | 2022 |
| ONESPAN 1927833 · TMA1217821 | OneSpan North America Inc. | 9 Electronics38 Telecommunications42 Science+1 | Registered | 2024 |
| OMNICABLE 1925234 · TMA1106330 | Omni Cable Corporation | 35 Advertising | Registered | 2021 |