| ORIMADE 2086500 · TMA1168763 | Owner not shown | 21 Housewares | Registered | 2023 |
| ORAMD 2021624 · TMA1167679 | Trusted Health Products, Inc. | 3 Cosmetics21 Housewares | Registered | 2023 |
| OREANDER 2021082 · TMA1157134 | an individual | 14 Jewellery | Registered | 2022 |
| ORMETRICS 1995615 · TMA1121628 | an individual | 9 Electronics35 Advertising42 Science | Registered | 2022 |
| ORIENT 1954109 · TMA1226417 · design | an individual | 29 Meat30 Coffee | Registered | 2024 |
| OUIAREMTL 1938619 · TMA1144044 | an individual | 18 Leather21 Housewares25 Clothing | Registered | 2022 |
| ORIENTEE 1902027 · TMA1077670 · design | an individual | 43 Restaurants | Registered | 2020 |
| ORIANTHA 1812688 · TMA1027029 | AbbVie Inc. | 5 Pharmaceuticals | Registered | 2019 |
| ORNATIVE 1798636 · TMA1022044 | ORNATIVE TABLEWARE INC. | 8 Hand21 Housewares24 Textiles | Registered | 2019 |
| ORONDIS 1785719 · TMA975673 · design | an individual | 5 Pharmaceuticals | Registered | 2017 |
| ORIENTO 1739363 · TMA960071 | TAOUTEL CANADA INC. | 34 Tobacco | Registered | 2017 |
| ORONDIS 1712606 · TMA964819 | an individual | 5 Pharmaceuticals | Registered | 2017 |
| ORENDA 1646314 · TMA909528 | Magellan Aerospace Limited | 7 Machines16 Paper37 Construction | Registered | 2015 |
| ORIENTAL 1622665 · TMA1002380 | DECOR GRATES INCORPORATED | 11 Lighting | Registered | 2018 |
| ORIENT 1599934 · TMA870046 · design | Orient Fan Company | 11 Lighting | Registered | 2014 |
| OrientXpress 1582285 · TMA904694 | Owner not shown | 7 Machines37 Construction40 Treatment | Registered | 2015 |
| OrientAction 1484952 · TMA840073 | CERIC | 35 Advertising38 Telecommunications41 Education | Registered | 2013 |
| ORIENTRYSTAL 1461278 · TMA796041 | JINJING GROUP CO. LTD | 1 Chemicals6 Metal7 Machines+4 | Registered | 2011 |
| ORMIT 1446175 · TMA774771 · design | Blue Water Venture Fund III, LLC, a Delaware Limited Liability Company | 9 Electronics | Registered | 2010 |
| ORAMETRIX 1359044 · TMA773654 | Dentsply Sirona Orthodontics Inc. | 10 Medical42 Science44 Medical | Registered | 2010 |
| ORENDA 1215055 · TMA658964 | Orenda Automation Technologies Inc. | 7 Machines35 Advertising40 Treatment+1 | Registered | 2006 |
| ORIENTAL 1024184 · TMA584074 | Mandarin Oriental (UK) Limited | 35 Advertising36 Finance39 Transport+2 | Registered | 2003 |
| ORIENT 0992186 · NFLD2186 · design | SUSAN HOSIERY LIMITED | 25 Clothing | Registered | 1936 |
| ORMTA 0799670 · TMA468390 | THE ONTARIO REGISTERED MUSIC TEACHERS' ASSOCIATION | 35 Advertising | Registered | 1997 |
| ORENDA 0768635 · TMA467473 | Magellan Aerospace Limited | 7 Machines12 Vehicles16 Paper | Registered | 1996 |