| CLUSTER 1641411 · TMA914418 | Campus Communities Inc. | 16 Paper18 Leather21 Housewares+7 | Registered | 2015 |
| CLUSTER 0431506 · TMA249584 | SIEMENS HEALTHCARE DIAGNOSTICS INC. | 5 Pharmaceuticals | Registered | 1980 |
| Clusterspin 2109354 · TMA1177837 | RAW iGaming Limited | 9 Electronics28 Toys41 Education | Registered | 2023 |
| CLUSTERSTOR 2062022 · TMA1211650 | Hewlett Packard Enterprise Development LP | 9 Electronics | Registered | 2023 |
| ClusterPBX 1757886 · TMA973026 | an individual | 38 Telecommunications42 Science | Registered | 2017 |
| CLUSTAIRE 1309744 · TMA795171 | Bedding Acquisition, LLC | 20 Furniture | Registered | 2011 |
| CLUSTERLITE 1384718 · TMA745209 | NEONLITE ELECTRONIC & LIGHTING (H.K.) LIMITED a legal entity | 11 Lighting | Registered | 2009 |
| CLUSTERDUCK 2258724 | Prodigy Design Limited | 9 Electronics41 Education | Pending | 2023 |
| COLSTER 1743371 · TMA1026920 | Yeti Coolers, LLC | 21 Housewares | Registered | 2019 |
| CLASTEON 1151254 · TMA603502 | an individual | 5 Pharmaceuticals | Registered | 2004 |
| CLESTRA 0702635 · TMA420297 | an individual | 7 Machines9 Electronics11 Lighting | Registered | 1993 |
| CLESTRA 0592635 · TMA352285 | an individual | 2 Paints6 Metal17 Rubber+4 | Registered | 1989 |
| CLUSTERNOMICS 1467963 · TMA799650 | The Canada Life Assurance Company | 16 Paper | Registered | 2011 |
| CLUSTIFIER 0910059 | National Research Council of Canada | 1 Chemicals2 Paints3 Cosmetics+42 | Pending | 1998 |
| clistofer 2176540 · TMA1227113 | Shenzhen Weierxi Electronic Commerce Co.Ltd. | 21 Housewares | Registered | 2024 |
| CELESTEON 1866395 · TMA1024972 | an individual | 11 Lighting | Registered | 2019 |
| CELISTICS 1484485 · TMA866936 · design | an individual | 35 Advertising39 Transport | Registered | 2013 |
| CLICKSTER 0768622 · TMA455979 | Sanford, L.P. an Illinois limited partnership | 16 Paper | Registered | 1996 |
| CÉLESTINS 0118632 · TMDA37265 · design | an individual | 32 Beer | Registered | 1925 |
| CELLUSTAR 2353282 | Transcend Packaging Limited | 8 Hand16 Paper21 Housewares+2 | Pending | 2023 |
| CLOSETART 2069304 | Hebei Minmetals Co., Ltd. | 20 Furniture | Pending | 2020 |
| CLAUSTHALER 1879389 · TMA1069967 · design | Radeberger Gruppe Holding GmbH | 32 Beer | Registered | 2020 |
| CHOLESTEROX 0840609 · TMA508585 | Les Laboratoires Suisse Inc. | 5 Pharmaceuticals | Registered | 1999 |
| CLAUSTHALER 0738965 · TMA435404 | Radeberger Gruppe Holding GmbH | 32 Beer | Registered | 1994 |
| CALLKIT 2250318 · TMA1267444 | Owner not listed | 9 Electronics | Registered | 2024 |