| OXYLIGHT 2268699 | Raja Trading Company, Inc. | 10 Medical | Pending | 2023 |
| Oclassic 2160163 · TMA1204332 | Shenzhen Obuy Technology Co. Ltd | 11 Lighting | Registered | 2023 |
| OuisieLuxe 2160036 · TMA1212174 | an individual | 27 Carpets | Registered | 2023 |
| OUSOLZA 2108466 · TMA1159423 | Mitsubishi Tanabe Pharma Corporation | 5 Pharmaceuticals | Registered | 2023 |
| OCCLUSAFE 2023202 · TMA1263809 | TERUMO CLINICAL SUPPLY KABUSHIKI KAISHA (TERUMO CLINICAL SUPPLY CO., LTD.) | 10 Medical | Registered | 2024 |
| OCULUS 1875199 · TMA1107773 | Facebook Technologies, LLC | 9 Electronics25 Clothing28 Toys+6 | Registered | 2021 |
| OglyZOR 1862398 · TMA1038583 | an individual | 1 Chemicals5 Pharmaceuticals | Registered | 2019 |
| OXYLIS 1826513 · TMA1024269 | Agro-Bio Contrôle inc | 5 Pharmaceuticals | Registered | 2019 |
| OGOLOGO 1815278 · TMA1054983 | an individual | 9 Electronics35 Advertising41 Education+1 | Registered | 2019 |
| OWAcliq 1805871 · TMA1097604 | Odenwald Faserplattenwerk GmbH | 6 Metal | Registered | 2021 |
| OZALYS 1757076 · TMA1033128 | Owner not shown | 3 Cosmetics25 Clothing44 Medical | Registered | 2019 |
| OCULUS 1732058 · TMA1038488 | Facebook Technologies, LLC | 25 Clothing35 Advertising38 Telecommunications+3 | Registered | 2019 |
| OSHLAG 1722258 · TMA966727 | 9321-8477 Québec Inc. dba Brasserie et Distillerie Oshlag | 32 Beer | Registered | 2017 |
| OCULUS 1660257 · TMA924802 | Facebook Technologies, LLC | 42 Science | Registered | 2016 |
| OCULUS 1660256 · TMA892834 | Meta Platforms, Inc. | 28 Toys | Registered | 2014 |
| OCULUS 1660255 · TMA892835 | Facebook Technologies, LLC | 9 Electronics | Registered | 2014 |
| OCULUS 1491617 · TMA857989 | D. E. Shaw & Co., L.P. | 36 Finance | Registered | 2013 |
| OCLC 1360953 · TMA778157 · design | OCLC, INC. | 9 Electronics38 Telecommunications41 Education+1 | Registered | 2010 |
| OUCHLESS 1197541 · TMA676305 | GOODY PRODUCTS, INC. | 21 Housewares26 Sewing | Registered | 2006 |
| OUCHLESS 1165045 · TMA624111 | GOODY PRODUCTS, INC. | 26 Sewing | Registered | 2004 |
| OCULUS 1071955 · TMA571418 | MARK ANTHONY GROUP INC. | 33 Wine | Registered | 2002 |
| OCLC 0669360 · TMA388827 | OCLC, INC. | 9 Electronics41 Education | Registered | 1991 |
| OSCILLOCOCCINUM 0661558 · TMA410610 | ANASYOR - USA CORPORATION | 5 Pharmaceuticals | Registered | 1993 |
| OCULUS 0658598 · TMA444447 · design | Groupe René Marchand Inc. | 35 Advertising | Registered | 1995 |
| OCULUS 0649244 · TMA445486 | Groupe René Marchand Inc. | 35 Advertising | Registered | 1995 |