A critical and systematic revision of the species composition of microphytobenthos of the northwestern part of the Black Sea was made. The author conducted long-term research (1980–2021), as well as analyzed retrospective data. In total, 524 species of microphytobenthos were found in the northwestern part of the Black Sea, which belong to 185 genera, 99 families, 53 orders, 12 classes, 8 divisions, 4 kingdoms, and 2 empires (domains). Representatives of division Bacillariophyta (413 rank first followed by prevalied over such Cyanoprokaryota (57), Chlorophyta (27), Miozoa (16), Euglenozoa (4), Ochrophyta (4), Haptophyta (2) and Charophyta (1). Nine species are new for the North-Western water area, 8 new species (Rhabdogloea smithii (R. et F. Chodat) Komárek, Cyanothece aeruginosa (Nägeli) Komárek, Calothrsx nidulans Setchell et N.L. Gardner, Fallacia nummularia (Grev.) D.G. Mann, Amphora kujalnitzkensis, Pinnularia brauniana (Grunow) Mills, Geissleria ignota (Krasske) Lange-Bert. et Metzeltin, Euglena satelles Brasl.-Spect.) of algae are represented for the Black Sea water area. Fifteen species were recorded as rare taxa for the North-Western part of the Black Sea. In the course of the revizion of the species composition of the Black Sea flora, 7 new taxonomic combinations of microscopic algae have been proposed.