| Navicula charlatii M. Perag., 1921 |
| Navicula cincta (Ehrenb.) Ralfs, 1861 |
| Navicula cincta var. cari (Ehrenb.) Cleve, 1895 |
| Navicula cincta var. cincta (Ehrenb.) Ralfs, 1861 |
| Navicula cincta var. heufleri (Grunow) Van Heurck, 1885 |
| Navicula circumtexta Meister & Hust., 1934 |
| Navicula clamans Hust., 1939 |
| Navicula clavata W. Greg., 1856 |
| Navicula clementis Grunow, 1882 |
| Navicula coarctata A. Schmidt, 1875 |
| Navicula cocconeiformis Greg. ex Grev., 1855 |
| Navicula confecta A. Schmidt, 1875 |
| Navicula confervacea (Kütz.) Grunow, 1880 |
| Navicula confervacea var. confervacea (Kütz.) Grunow, 1880 |
| Navicula contenta Grunow, 1885 |
| Navicula couperi (Bailey) Ralfs, 1861 |
| Navicula crabroniformis Grunow, 1875 |
| Navicula crucicula (W. Sm.) Donk., 1871 |
| Navicula cruciculoides Brockmann, 1950 |
| Navicula cryptocephala Kütz., 1844 |