| ONTEX 1817991 · TMA1010790 · design | Owner not shown | 5 Pharmaceuticals16 Paper | Registered | 2018 |
| ONTEX 1817989 · TMA1010500 | Owner not shown | 3 Cosmetics5 Pharmaceuticals16 Paper | Registered | 2018 |
| ONTEX 2030282 | an individual | 17 Rubber | Pending | 2020 |
| ONETest 1987497 · TMA1131511 | Fusion Genomics Corporation | 1 Chemicals5 Pharmaceuticals44 Medical | Registered | 2022 |
| ONETEX 1431117 · TMA783210 | Rimex Metals Group Ltd. | 6 Metal21 Housewares24 Textiles | Registered | 2010 |
| ONDEX 0493164 · TMA312221 | SIFMAR SA | 19 Building | Registered | 1986 |
| ONTESOL 2067456 | Ontesol.com Inc. | 41 Education | Pending | 2020 |
| Ontaki 2227810 · TMA1253838 | Owner not shown | 8 Hand | Registered | 2024 |
| ONDECK 2184553 · TMA1231370 | Corteva Agriscience LLC | 5 Pharmaceuticals | Registered | 2024 |
| ONDOG 2159244 · TMA1210011 · design | Anhaorui Electronics Co. Limited | 9 Electronics | Registered | 2023 |
| OMTEKNI 2156109 · TMA1191126 | GLAXO GROUP LIMITED | 5 Pharmaceuticals | Registered | 2023 |
| OMTECH 2117382 · TMA1210768 · design | Shanghai Yunhui Trading Co. Ltd. | 7 Machines | Registered | 2023 |
| ONEHOUDES 2111734 · TMA1187480 | Zhongshan Yijian Fangzi Trading Co. Ltd. | 11 Lighting | Registered | 2023 |
| OneTag 2108482 · TMA1219046 | BlueCats Australia Pty Limited | 9 Electronics | Registered | 2024 |
| ONTOZRY 2069963 · TMA1204866 | SK BIOPHARMACEUTICALS CO. LTD. | 5 Pharmaceuticals | Registered | 2023 |
| ondesignca 2019964 · TMA1132199 | Owner not shown | 42 Science | Registered | 2022 |
| OnWatch 2005436 · TMA1128416 | Owner not shown | 9 Electronics | Registered | 2022 |
| OWNIT1ST 1995551 · TMA1125066 | an individual | 14 Jewellery26 Sewing | Registered | 2022 |
| ONETAK 1964913 · TMA1128600 | an individual | 9 Electronics12 Vehicles | Registered | 2022 |
| ONETAQ 1941289 · TMA1188995 | New England Biolabs Inc. | 1 Chemicals | Registered | 2023 |
| OMETZ 1936964 · TMA1122135 | an individual | 9 Electronics16 Paper21 Housewares+7 | Registered | 2022 |
| ONETIGRIS 1904006 · TMA1077135 · design | Shenzhen Wanghe Technology Co. Ltd. | 9 Electronics13 Firearms18 Leather+3 | Registered | 2020 |
| ONDEXXYA 1889840 · TMA1085129 | Portola Pharmaceuticals, Inc. | 5 Pharmaceuticals | Registered | 2020 |
| OUINMÈTSÉ 1864583 · TMA1089462 | an individual | 38 Telecommunications41 Education | Registered | 2020 |
| OnDisplay 1833259 · TMA1045996 | CASCADES CANADA ULC | 3 Cosmetics5 Pharmaceuticals16 Paper+5 | Registered | 2019 |