Seventy-two species of marine plants, all but two of which are algal species, are listed from the Suez Canal water system. Of these, 52 have not been recorded previously from the Suez Canal. Twelve of the newly recorded species are green algae, four are diatoms, eight are brown algae, eight are blue-greens and 21 are red algae. Of the 99 plant species reported from the Suez Canal since it was opened about a century ago, 47 are known from both the eastern Mediterranean and the northern Red Sea, 24 have been reported from the northern Red Sea but not from the eastern Mediterranean, 14 have been reported from the eastern Mediterranean and not from the Red Sea, and 14 have been found in the Suez Canal but not yet in both the eastern Mediterranean and the northern Red Sea. New and previously reported stations in the Suez Canal, as well as ecological remarks and notes on the occurrence of each species in the eastern Mediterranean and the northern Red Sea are given. The nature of Suez Canal flora, the changes in floral assemblage in the Canal, the migration of plant species from the Red Sea into the Mediterranean in the light of the new records from the Suez Canal, and the role of the Canal as a barrier for the migration of algae, are discussed.