| Ozavyher 2167218 · TMA1210118 | Daiichi Sankyo Company, Limited | 5 Pharmaceuticals | Registered | 2023 |
| OXYPRESSOR 2121497 · TMA1270992 | Poseidon Ocean Systems Ltd. | 7 Machines11 Lighting | Registered | 2024 |
| OXFORE 2109739 · TMA1159431 | an individual | 9 Electronics | Registered | 2023 |
| Oxbury 2019315 · TMA1153969 | Oxbury FS Plc | 9 Electronics16 Paper35 Advertising+3 | Registered | 2022 |
| OXBRYTA 2002209 · TMA1088441 · design | Global Blood Therapeutics, Inc. | 5 Pharmaceuticals | Registered | 2020 |
| OOGIEBEAR 1921996 · TMA1101569 | OOGIE SOLUTIONS LLC | 10 Medical21 Housewares | Registered | 2021 |
| OXFORD 1908888 · TMA1116461 | HISTON SWEET SPREADS LIMITED | 29 Meat | Registered | 2021 |
| OXBRYTA 1903493 · TMA1085133 | Global Blood Therapeutics, Inc. | 5 Pharmaceuticals | Registered | 2020 |
| OXFORD 1859242 · TMA1109840 | Oxford Global Resources, LLC | 35 Advertising42 Science | Registered | 2021 |
| OCUVERA 1792890 · TMA1044409 | OCUVERA LLC | 42 Science | Registered | 2019 |
| OZAPIRA 1777364 · TMA1001892 | RECEPTOS LLC | 5 Pharmaceuticals | Registered | 2018 |
| OGIVRI 1776748 · TMA1035060 | Biosimilars Newco Limited | 5 Pharmaceuticals | Registered | 2019 |
| OSPREY 1761607 · TMA969164 · design | Sandvik Osprey Ltd. | 6 Metal40 Treatment | Registered | 2017 |
| OSPREY 1761606 · TMA969161 | Sandvik Osprey Ltd. | 6 Metal40 Treatment | Registered | 2017 |
| OspreyFMS 1743087 · TMA993095 | Quest Controls, Inc. | 9 Electronics42 Science | Registered | 2018 |
| OXPURE 1737720 · TMA1000922 | Oxbow Activated Carbon LLC | 1 Chemicals | Registered | 2018 |
| OXFORD 1679648 · TMA948509 | Stelpro Design Inc. | 11 Lighting | Registered | 2016 |
| OXBORO 1635961 · TMA943336 | Aspen Surgical Products, Inc. a Michigan corporation | 10 Medical | Registered | 2016 |
| OSFERION 1579601 · TMA968169 | Olympus Terumo Biomaterials Corp. a Japanese joint-stock company | 5 Pharmaceuticals10 Medical | Registered | 2017 |
| OXFORD 1558115 · TMA917820 | The Chancellor Masters and Scholars of the University of Oxford (trading as Oxford University Press) | 9 Electronics16 Paper27 Carpets+1 | Registered | 2015 |
| OXYPRO 1502414 · TMA807738 | BISSELL Inc. | 3 Cosmetics | Registered | 2011 |
| OSPREY 1483988 · TMA863985 · design | Osprey Packs, Inc. | 16 Paper18 Leather21 Housewares+2 | Registered | 2013 |
| OSPREY 1483927 · TMA844698 · design | Osprey Packs, Inc. | 18 Leather | Registered | 2013 |
| O2Saver 1451526 · TMA914353 | an individual | 9 Electronics | Registered | 2015 |
| OSSEOPERM 1410594 · TMA808044 | Merit Medical Systems, Inc. | 5 Pharmaceuticals | Registered | 2011 |