Marine algae (Seaweeds) are photosynthetic organisms living in seas and oceans. They are known to have several benefits and are recognized as a source of several important bioactive compounds. In the present review, we present brief information concerning marine algae, their classification, distribution, and importance. Also, we are focusing on studies concerning marine algae collected from Egyptian coasts. The review highlights the important studies concerned by evaluating the bioactivity and chemical composition of marine algae in Egypt. The present review contains the main results of experimental studies discussing the antioxidant, antibacterial and anti-cancer activities of seaweeds. It also contains principle results for studies about the use of seaweed biomass as adsorbents for water treatment and as environmental pollution bio-monitors. The data provided in this review offer a scientific background about marine algae in Egypt that could be very helpful for researchers working in this area.