| ONGO 1953726 · TMA1199513 | CBRS Alliance Non-Profit Mutual Benefit Corporation | 9 Electronics42 Science | Registered | 2023 |
| ONGO 1953716 · TMA1199512 · design | CBRS Alliance Non-Profit Mutual Benefit Corporation | 9 Electronics42 Science | Registered | 2023 |
| ONGA 1637519 · TMA890213 · design | Enbridge Gas Inc. | 35 Advertising38 Telecommunications41 Education+1 | Registered | 2014 |
| ONC 0634661 · TMA374593 | NITREX METAL INC. | 40 Treatment | Registered | 1990 |
| ONEC 2104641 | ONEC Construction Inc. | 37 Construction42 Science | Pending | 2021 |
| ONIGA 1707053 · TMA929152 | MODE AVALANCHE INC. | 25 Clothing | Registered | 2016 |
| ONEGO 1504972 · TMA881162 | ONEGO, INC. | 35 Advertising36 Finance39 Transport+3 | Registered | 2014 |
| ONEGO 1417142 · TMA801705 | ONEGO, INC. | 35 Advertising36 Finance37 Construction+3 | Registered | 2011 |
| OMNIC@ 1184134 · TMA619780 · design | OMNICHEM INC. | 9 Electronics | Registered | 2004 |
| OINGS 0991463 · NFLD1463 · design | General Motors LLC | 12 Vehicles | Registered | 1927 |
| ONEAC 0490858 · TMA280768 | Powervar, Inc. | 9 Electronics | Registered | 1983 |
| ONEUC 2118547 | Oneuc LLC | 42 Science | Pending | 2021 |
| Onica 1960979 | Onica Technologies Canada, Inc. | 42 Science | Pending | 2019 |
| ONEEKK 2266021 · TMA1285027 | Shenzhen Benbenxiang Electronic Commerce Co. Ltd. | 21 Housewares | Registered | 2025 |
| OHMNIS 2260541 · TMA1281121 · design | Ohmnis Inc. Joseph Kasumba, Blavasky Kasumba | 35 Advertising42 Science | Registered | 2025 |
| OMG 2257529 · TMA1267506 · design | OMG OASIS MEDITERRANEAN GRILL LTD. | 35 Advertising43 Restaurants | Registered | 2024 |
| Oinsi 2256199 · TMA1276183 | an individual | 14 Jewellery | Registered | 2024 |
| ONEYUS 2233734 · TMA1256667 · design | Shenzhen Aoyin Lighting Co. Ltd | 20 Furniture | Registered | 2024 |
| OMEGA 2230572 · TMA1245662 · design | an individual | 9 Electronics | Registered | 2024 |
| OMNIAGEO 2215933 · TMA1202041 | OMNIAGEO Inc. | 42 Science | Registered | 2023 |
| ONYX 2191511 · TMA1233841 | Owner not shown | 35 Advertising44 Medical | Registered | 2024 |
| OMOJI 2186481 · TMA1284476 · design | GUANGDONG OPPO MOBILE TELECOMMUNICATIONS CORP. LTD. | 9 Electronics | Registered | 2025 |
| ONESIE 2186469 · TMA1223854 | Owner not shown | 12 Vehicles | Registered | 2024 |
| OWIMX 2169070 · TMA1219920 | Shenzhen Yehong Electronic Commerce Co. Ltd. | 21 Housewares | Registered | 2024 |
| ONCAI 2157827 · TMA1218367 · design | Shenzhen Yichen Shidai Trading Co. Ltd. | 25 Clothing | Registered | 2024 |