| OMNICAT 1768202 · TMA978162 | an individual | 1 Chemicals | Registered | 2017 |
| OMNICUT 1557071 · TMA1027312 | Owner not shown | 10 Medical | Registered | 2019 |
| ONEKIT 2130454 | O'Neil Digital Solutions, LLC (a California limited liability company) | 42 Science | Pending | 2021 |
| ONEKIT 2130452 · design | O'Neil Digital Solutions, LLC (a California limited liability company) | 42 Science | Pending | 2021 |
| OMNICATH 1680927 · TMA1063261 | an individual | 10 Medical | Registered | 2019 |
| OMNISET 1680917 · TMA1063253 | an individual | 10 Medical | Registered | 2019 |
| OMNIACT 1493270 · TMA947357 | CORPORATEK INC. | 9 Electronics42 Science | Registered | 2016 |
| ONESUIT 1273706 · TMA715975 | Saint-Gobain Performance Plastics Corporation | 9 Electronics | Registered | 2008 |
| OMNIJET 1195913 · TMA678675 | Ilford Imaging Europe GmbH | 16 Paper | Registered | 2006 |
| OmicGot 2269685 | HUIZHOU YUMIN NETWORK TECHNOLOGY CO. LTD. | 25 Clothing | Pending | 2023 |
| OMNISCOUT 1460613 · TMA803332 | Worldscout Corporation | 9 Electronics38 Telecommunications39 Transport+2 | Registered | 2011 |
| ONCOTERRA 2217074 · TMA1235265 | Phase Genomics, Inc. | 42 Science | Registered | 2024 |
| OMGTMD 2177941 · TMA1227273 | an individual | 6 Metal | Registered | 2024 |
| OneStock 2177427 · TMA1278840 | OneStock | 42 Science | Registered | 2024 |
| ONESAT 2170045 · TMA1204341 | Owner not shown | 9 Electronics | Registered | 2023 |
| ONSTIN 2137448 · TMA1220442 | NUTRA STANDARD INC | 5 Pharmaceuticals | Registered | 2024 |
| ownest 2133469 · TMA1196912 | Guangzhou Yunhan Xiangfeng Network Technology Co. Ltd. | 9 Electronics | Registered | 2023 |
| OnkoDisruptor 2129418 · TMA1195788 | an individual | 10 Medical | Registered | 2023 |
| ONESTREAM 2114513 · TMA1228780 | OneStream Software LLC | 9 Electronics35 Advertising41 Education+1 | Registered | 2024 |
| OMIGHTY 2108361 · TMA1139904 · design | FOKDA POPO PTE LTD | 18 Leather25 Clothing35 Advertising | Registered | 2022 |
| Omistor 2102031 · TMA1175823 | an individual | 20 Furniture | Registered | 2023 |
| ONSTAR 2095726 · TMA1250745 | Onstar LLC | 36 Finance | Registered | 2024 |
| ONESTAR 2094875 · TMA1172531 · design | Ming Shin Tools Co. Ltd. | 8 Hand | Registered | 2023 |
| OMIGHTY 2075608 · TMA1152054 · design | FOKDA POPO PTE LTD | 25 Clothing | Registered | 2022 |
| ONCOADVANCES 2068648 · TMA1280236 | American Association for Cancer Research, Inc. | 16 Paper41 Education42 Science | Registered | 2025 |