| OTA 2110222 | ONTARIO TRUCKING ASSOCIATION | 9 Electronics16 Paper35 Advertising+3 | Pending | 2021 |
| OTTA 1966778 | 10X Innovation GmbH & Co. KG | 11 Lighting21 Housewares30 Coffee+3 | Pending | 2019 |
| OTH 0907958 · design | THE ONTARIO EDUCATIONAL COMMUNICATIONS AUTHORITY | 1 Chemicals2 Paints3 Cosmetics+42 | Pending | 1996 |
| OTHWAY 2037880 · TMA1164332 · design | Shenzhen Hongyada E-Commerce Co. Ltd | 27 Carpets | Registered | 2023 |
| OTHWAY 2037879 · TMA1164331 · design | Shenzhen Hongyada E-Commerce Co. Ltd | 11 Lighting | Registered | 2023 |
| ODAYA 2212499 · TMA1223307 | AGENCE TINGG INC. | 4 Oils5 Pharmaceuticals10 Medical | Registered | 2024 |
| Otai 2211794 · TMA1243016 | Huizhou Outai Home Furnishing Co., Ltd. | 24 Textiles | Registered | 2024 |
| OTWD 2205719 · TMA1257868 · design | Off The Wall Displays Inc. | 11 Lighting20 Furniture | Registered | 2024 |
| ODEA 2188378 · TMA1232682 · design | ZHEJIANG ODEAR SPORTS GOODS CO.LTD | 28 Toys | Registered | 2024 |
| Oduio 2187071 · TMA1223206 | Shenzhen Xingaichen Trading CO. LTD. | 9 Electronics14 Jewellery28 Toys | Registered | 2024 |
| OIDEA 2181663 · TMA1229567 | OUTSTANDING IDEA LIMITED | 14 Jewellery | Registered | 2024 |
| ÖÖD 2173232 · TMA1256285 · design | an individual | 19 Building43 Restaurants | Registered | 2024 |
| OT 2167815 · TMA1277370 · design | OMNITRANS INC. | 16 Paper35 Advertising | Registered | 2024 |
| OUTDO 2152766 · TMA1188831 · design | XIAMEN MEGA KINGDOM TECHNOLOGY CO. LTD. | 9 Electronics | Registered | 2023 |
| ODE 2131357 · TMA1223692 | Fellow Industries Inc. | 7 Machines | Registered | 2024 |
| OUADO 2128662 · TMA1208563 | an individual | 25 Clothing | Registered | 2023 |
| OUTDEYA 2108470 · TMA1159427 | Mitsubishi Tanabe Pharma Corporation | 5 Pharmaceuticals | Registered | 2023 |
| ODDO 2105086 · TMA1196555 | an individual | 32 Beer33 Wine | Registered | 2023 |
| Oath 2087604 · TMA1170127 | HIGHBAR ENTERPRISES LTD. | 5 Pharmaceuticals | Registered | 2023 |
| ÖÖD 2084116 · TMA1247840 · design | an individual | 19 Building | Registered | 2024 |
| OTE 2081410 · TMA1174692 | OTE Household Appliances (Shenzhen) Co. Ltd | 7 Machines11 Lighting | Registered | 2023 |
| O8T 2077417 · TMA1204893 | Omniscient Neurotechnology Pty Limited | 9 Electronics42 Science | Registered | 2023 |
| OTE 2076360 · TMA1143844 | Owner not shown | 25 Clothing35 Advertising | Registered | 2022 |
| OT 2067439 · TMA1268204 · design | Owner not shown | 16 Paper21 Housewares25 Clothing+2 | Registered | 2024 |
| OTTO 2041077 · TMA1142839 · design | Owner not shown | 8 Hand | Registered | 2022 |