| Nitzschia fibulafissa Lange-Bert., 1980 |
| Nitzschia filiformis (W. Sm.) Hust., 1896 |
| Nitzschia filiformis var. genuina Cleve-Euler, 1952 |
| Nitzschia flexa Schumann, 1862 |
| Nitzschia flexoides Geitler, 1968 |
| Nitzschia fluminensis Grunow, 1862 |
| Nitzschia fonticola (Grunow) Grunow, 1881 |
| Nitzschia fonticola var. capitata A. Cleve |
| Nitzschia fonticola var. pelagica Hust., 1924 |
| Nitzschia fossilis (Grunow) Grunow, 1881 |
| Nitzschia fraudulenta Cleve, 1897 |
| Nitzschia frigida Grunow, 1880 |
| Nitzschia frustulum (Kütz.) Grunow, 1880 |
| Nitzschia frustulum var. frustulum (Kütz.) Grunow, 1880 |
| Nitzschia frustulum var. inconspicua (Grunow) Grunow, 1878 |
| Nitzschia frustulum var. perminutum Grunow, 1881 |
| Nitzschia frustulum var. perpusilla (Rabenhorst) Van Heurck, 1885 |
| Nitzschia fruticosa Hust., 1957 |
| Nitzschia fusiformis Grunow, 1880 |
| Nitzschia gandersheimiensis Krasske, 1927 |