| OCAM 0901662 | ONTARIO CENTRE FOR ADVANCED MANUFACTURING | 1 Chemicals2 Paints3 Cosmetics+42 | Pending | 1984 |
| OCHAME 2058240 · TMA1194542 | Godspeed Brewery Inc. | 32 Beer35 Advertising | Registered | 2023 |
| OAKHAM 2313823 | CONNECT CREATIVE LIMITED | 20 Furniture | Pending | 2024 |
| OKAN 2171628 · TMA1169173 | SAULE LLC | 9 Electronics | Registered | 2023 |
| OCUM 2155536 · TMA1187882 | N.B. Automation inc. | 42 Science | Registered | 2023 |
| OCIM 2140005 · TMA1268287 | an individual | 14 Jewellery35 Advertising36 Finance+1 | Registered | 2024 |
| OCIM 2101496 · TMA1180474 | an individual | 36 Finance | Registered | 2023 |
| OCEAN 2056861 · TMA1283950 | Azul 3D, Inc. | 7 Machines40 Treatment | Registered | 2025 |
| OCOM 2016949 · TMA1224771 | an individual | 37 Construction38 Telecommunications42 Science | Registered | 2024 |
| OCAN 2002001 · TMA1131558 | an individual | 5 Pharmaceuticals | Registered | 2022 |
| OCEAN 1999509 · TMA1117475 · combined | Hawaii Sea Spirits, LLC | 33 Wine | Registered | 2022 |
| OCEAN 1899885 · TMA1088412 | Hawaii Sea Spirits, LLC | 33 Wine | Registered | 2020 |
| OCEAN 1847063 · TMA1070161 · design | Public Joint Stock Company Gazprom Neft | 4 Oils | Registered | 2020 |
| OXAM 1638308 · TMA912041 | THE OXFORD ASSET MANAGEMENT COMPANY LIMITED a United Kingdom company | 36 Finance | Registered | 2015 |
| OKAMI 1609117 · TMA902788 | Fuji Food Products, Inc. | 29 Meat30 Coffee | Registered | 2015 |
| OGAM 1576066 · TMA870173 | Orchard Global Capital Group (S) Pte Ltd | 36 Finance | Registered | 2014 |
| OCEAN 1454236 · TMA825572 · design | LEHIGH HANSON MATERIALS LIMITED | 7 Machines11 Lighting17 Rubber+1 | Registered | 2012 |
| OKAMI 1447882 · TMA798186 | Murata Power Solutions, Inc. | 9 Electronics | Registered | 2011 |
| OCEAN 1429419 · TMA825582 | LEHIGH HANSON MATERIALS LIMITED | 7 Machines11 Lighting17 Rubber+1 | Registered | 2012 |
| OCEAN 1381484 · TMA740170 | Schlumberger Canada Limited | 9 Electronics42 Science | Registered | 2009 |
| OCEAN 1346143 · TMA730340 | Oceanside Equipment Limited | 6 Metal7 Machines8 Hand | Registered | 2008 |
| OCEAN 1301484 · TMA698878 | ATRIUM MEDICAL CORPORATION, a legal entity | 10 Medical | Registered | 2007 |
| OKAMI 1259602 · TMA715232 · design | CAPCOM CO., LTD | 9 Electronics28 Toys | Registered | 2008 |
| OCEAN 1115073 · TMA585161 | Flame Control Coatings, LLC | 2 Paints | Registered | 2003 |
| OCEAN 0991252 · NFLD1252 | THE STANDARD MANUFACTURING COMPANY LIMITED | 1 Chemicals2 Paints10 Medical+2 | Registered | 1924 |