| Nitzschia garrensis Hust., 1950 |
| Nitzschia graciliformis Lange-Bert. & Simonsen, 1978 |
| Nitzschia gracilis Hantzsch, 1860 |
| Nitzschia grana M.H. Hohn & Hellerman, 1966 |
| Nitzschia granulata Grunow, 1880 |
| Nitzschia grossestriata Hust., 1955 |
| Nitzschia gruendleri Grunow, 1878 |
| Nitzschia grunowii Hasle, 1972 |
| Nitzschia habirshawii Febiger ex Cleve & Möller, 1879 |
| Nitzschia hantzschiana Rabenh., 1860 |
| Nitzschia heufleriana Grunow, 1862 |
| Nitzschia holsatica Hust., 1924 |
| Nitzschia homburgiensis Lange-Bert., 1978 |
| Nitzschia hungarica Grunow, 1862 |
| Nitzschia hustedtiana Salah, 1953 |
| Nitzschia hybrida Grunow, 1880 |
| Nitzschia incerta (Grunow) M.Peragallo, 1903 |
| Nitzschia incognita Legler & Krasske, 1940 |
| Nitzschia inconspicua Grunow, 1862 |
| Nitzschia incrustans Grunow, 1862 |