| OneCem 2134167 · TMA1240962 | Holcim Technology Ltd | 19 Building | Registered | 2024 |
| ONOCON 2095727 · design | Onocon Developments Ltd. | 36 Finance37 Construction39 Transport+1 | Pending | 2021 |
| ONECOMMAND 1448639 · TMA832447 | Emulex Design & Manufacturing Corporation | 9 Electronics | Registered | 2012 |
| ONCOMMAND 1764138 · TMA999637 | OCC Technologies, LLC | 9 Electronics35 Advertising37 Construction+1 | Registered | 2018 |
| ONCOMMAND 1448732 · TMA770485 | Hayward Industries, Inc. | 9 Electronics | Registered | 2010 |
| ONECHANGE 1393463 · TMA753049 | OneChange Foundation | 11 Lighting25 Clothing35 Advertising+2 | Registered | 2009 |
| ONECHANGE 1393449 · TMA752571 · design | OneChange Foundation | 11 Lighting25 Clothing35 Advertising+2 | Registered | 2009 |
| ONEAGENT 2141675 · TMA1250808 | Dynatrace LLC | 9 Electronics | Registered | 2024 |
| OMOZEN 2050879 · TMA1167986 · design | an individual | 21 Housewares | Registered | 2023 |
| ONSON 2032896 · TMA1139663 | Shenzhen Weizhisheng E-Commerce Co.Ltd. | 7 Machines | Registered | 2022 |
| ONSON 2003667 · TMA1143464 · design | Shenzhen Weizhisheng E-Commerce Co.Ltd. | 7 Machines | Registered | 2022 |
| ONECONTENT 1955730 · TMA1267664 | HYLAND SOFTWARE, INC. | 9 Electronics42 Science | Registered | 2024 |
| ONSEN 1954250 · TMA1192262 · design | NuEnergy Distribution Inc. | 11 Lighting | Registered | 2023 |
| ONESAM 1910330 · TMA1086840 · design | Guangzhou Zheng Gong Niu Technology Co. Ltd. | 9 Electronics | Registered | 2020 |
| OMCAN 1901457 · TMA1093961 | OMCAN MFG. & DISTRIBUTING CO. INC. | 7 Machines8 Hand11 Lighting+3 | Registered | 2021 |
| ONESUN 1827591 · TMA1013821 · design | Alternative Eyewear Inc. | 9 Electronics | Registered | 2019 |
| ONECONNECT 1769034 · TMA1037355 | Panasonic Corporation of North America | 35 Advertising38 Telecommunications41 Education | Registered | 2019 |
| ONYXEN 1714004 · TMA950207 | an individual | 1 Chemicals | Registered | 2016 |
| ONEGIN 1708158 · TMA1036834 | Owner not shown | 32 Beer33 Wine35 Advertising+2 | Registered | 2019 |
| ONECONNECT 1448638 · TMA832448 | Emulex Design & Manufacturing Corporation | 9 Electronics | Registered | 2012 |
| ONEXONE 1357631 · TMA772818 | ONEXONE Foundation | 14 Jewellery25 Clothing | Registered | 2010 |
| ONEXONE 1351887 · TMA717690 · design | ONEXONE Foundation | 35 Advertising | Registered | 2008 |
| ONEXONE 1260745 · TMA664818 | ONEXONE Foundation | 35 Advertising | Registered | 2006 |
| OMNISCAN 1163808 · TMA629574 | Olympus NDT Canada inc. | 9 Electronics | Registered | 2005 |
| OMNISCAN 0694296 · TMA421687 | an individual | 5 Pharmaceuticals | Registered | 1993 |