| Navicula incomposita Hagelst., 1939 |
| Navicula intercedens A. Schmidt, 1890 |
| Navicula intermedia Lagerh., 1873 |
| Navicula interrupta (W. Sm.) A. Schmidt, 1876 |
| Navicula lacrimans A. Schmidt, 1875 |
| Navicula lacustris W. Greg., 1856 |
| Navicula laevissima Kütz., 1844 |
| Navicula lanceolata (C. Agardh) Kütz., 1844 |
| Navicula lanceolata var. genuina Meister, 1912 |
| Navicula lapidosa Krasske, 1929 |
| Navicula lateropunctata J.H. Wallace, 1960 |
| Navicula laterostrata Hust., 1925 |
| Navicula latissima W. Greg., 1856 |
| Navicula latiuscula Kütz., 1844 |
| Navicula libellus W. Greg., 1857 |
| Navicula librele Ehrenb., 1832 |
| Navicula lineola Grunow, 1884 |
| Navicula lineola var. perlepida (Grunow) Cleve, 1894 |
| Navicula longa (W. Greg.) Ralfs ex A. Pritch., 1861 |
| Navicula longa var. irregularis Hust., 1955 |