| ONESPAN 1927833 · TMA1217821 | OneSpan North America Inc. | 9 Electronics38 Telecommunications42 Science+1 | Registered | 2024 |
| ONESAFE 1863535 · TMA1060576 | Tremco CPG Inc. | 2 Paints | Registered | 2019 |
| ONESAFE 1667843 · TMA980061 | Bunzl IP Holdings, LLC | 9 Electronics10 Medical21 Housewares | Registered | 2017 |
| OWNSPACE 2299579 | Owner not listed | 9 Electronics35 Advertising42 Science | Pending | 2023 |
| OWNSPACE 2299576 · design | OwnSpace Solutions Inc. | 9 Electronics35 Advertising42 Science | Pending | 2023 |
| ONESPEC 2266115 | CertainTeed LLC | 19 Building36 Finance37 Construction+2 | Pending | 2023 |
| ONESPARK 2036682 | Onespark (Pty) Ltd. | 9 Electronics35 Advertising36 Finance | Pending | 2020 |
| OMOOSPACE 2210855 · TMA1226378 | Studio Grand Design Inc. | 9 Electronics | Registered | 2024 |
| ONESPHERE 1880241 · TMA1094425 | Hewlett Packard Enterprise Development LP | 9 Electronics42 Science | Registered | 2021 |
| OMYASPACE 1506306 · TMA822337 | an individual | 1 Chemicals | Registered | 2012 |
| ONESPORT 2119011 · TMA1186396 · design | Dongguan onesport Technology Co. Ltd | 12 Vehicles | Registered | 2023 |
| ONESPOT 1406877 · TMA804130 · design | 2180792 Ontario Inc. | 6 Metal9 Electronics10 Medical+5 | Registered | 2011 |
| ONESPIN 1279225 · TMA701725 | Siemens Electronic Design Automation GmbH | 9 Electronics41 Education42 Science+1 | Registered | 2007 |
| ONESUBSEA 1662318 · TMA969787 | ONESUBSEA IP UK LIMITED A corporation organized and existing under the laws of the United Kingdom | 6 Metal7 Machines9 Electronics+8 | Registered | 2017 |
| ONCOPHAGE 1255314 · TMA789161 | Agenus Inc. | 5 Pharmaceuticals16 Paper44 Medical | Registered | 2011 |
| OMNISPARK 2330113 | Owner not listed | 7 Machines | Pending | 2024 |
| OMNISCAPE 2293592 | an individual | 11 Lighting | Pending | 2023 |
| ONCOPANEL 2197923 | Eurofins Panlabs, Inc. | 42 Science | Pending | 2022 |
| 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 |
| 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 |