| Omyamax 2255992 · TMA1274681 | an individual | 1 Chemicals | Registered | 2024 |
| ONINAKI 1973567 · TMA1184638 | Kabushiki Kaisha Square Enix Holdings (also trading as Square Enix Holdings Co., Ltd.) | 9 Electronics16 Paper28 Toys+1 | Registered | 2023 |
| ONEMAGNIFY 1897148 · TMA1083531 · design | Marketing Associates, LLC | 35 Advertising | Registered | 2020 |
| ONEMAGNIFY 1897147 · TMA1083530 | Marketing Associates, LLC | 35 Advertising | Registered | 2020 |
| ONIMUSHA 1891359 · TMA1081117 | CAPCOM CO., LTD | 41 Education | Registered | 2020 |
| OMNIANGLE 1878941 · TMA1067243 | Prym Consumer USA Inc. | 9 Electronics | Registered | 2019 |
| ONIONS 52 1873096 · TMA1063899 | Onions 52, Inc. | 31 Fresh | Registered | 2019 |
| OMNIMOC 1861857 · TMA1048508 · design | Eastman Footwear Corp. | 18 Leather25 Clothing | Registered | 2019 |
| OneMeasure 1857098 · TMA1048313 | Global Wireless Solutions, Inc. | 9 Electronics | Registered | 2019 |
| OMAMIST 1850409 · TMA1039877 | The Ddrops Company Inc. | 5 Pharmaceuticals | Registered | 2019 |
| OMNIMAX 1822154 · TMA1094873 | Omnimax International, Inc. | 40 Treatment | Registered | 2021 |
| ONEMOS 1728857 · TMA953599 · design | SHENZHEN RAMOS DIGITAL TECHNOLOGY CO. LTD. | 9 Electronics20 Furniture | Registered | 2016 |
| OMNIMASK 1674526 · TMA941789 | omniTECHNIK Mikroverkapselungs GmbH | 1 Chemicals | Registered | 2016 |
| ONENECK 1658121 · TMA954573 | OneNeck IT Solutions LLC | 38 Telecommunications42 Science | Registered | 2016 |
| OmniMax 1575118 · TMA904191 | an individual | 35 Advertising | Registered | 2015 |
| OwningSocial 1568934 · TMA854748 | Resort Owners Group Ltd. | 36 Finance | Registered | 2013 |
| ONENESS 1414439 · TMA811801 | OWA Holdings Ltd | 9 Electronics16 Paper41 Education+1 | Registered | 2011 |
| ONIMUSHA 1070165 · TMA568170 | CAPCOM CO., LTD | 9 Electronics16 Paper25 Clothing+1 | Registered | 2002 |
| OMNIMAX 0681852 · TMA401207 | LUSSIER CABINET DE SERVICES FINANCIERS INC. | 36 Finance | Registered | 1992 |
| OMNIMAX 0359464 · TMA199989 | IMAX CORPORATION | 9 Electronics | Registered | 1974 |
| ONEMIX 2345762 · design | Owner not listed | 25 Clothing | Pending | 2024 |
| OMENS 2297106 | an individual | 9 Electronics38 Telecommunications41 Education | Pending | 2023 |
| Omens 2291325 | an individual | 3 Cosmetics | Pending | 2023 |
| OMNIMICRO 2288068 | an individual | 10 Medical | Pending | 2023 |
| ONENEST 2239543 | Umano Medical World Inc. also doing business under the names of Umano Monde Médical and Umano Medical World | 10 Medical | Pending | 2023 |