This study aimed to evaluate total phenolics (TPC) and flavonoid (TFC) contents, antioxidant, antihemolytic, and antimicrobial properties of different seaweed ethanolic crude extracts that were collected from the Red Sea coast, Egypt. These extracts were obtained from ten different species of seaweeds including Padina boergesnii, Sargassum subrepandum M Alam, Sargassum subrepandum Hur, Sargassum aquifolium, Sargassum cinerum M Alam, and Sargassum cinerum Mangroove fromPheaophytae, Codium tomentosum, Dictyota dichotoma, and Halimeda opunta from Chlorophytae, and Laurancia papilosa from Rhodophytae. Furthermore, The ethanolic extracts were analyzed for total phenolic (TPC) and total flavonoid content (TFC),  the antioxidant activities including; 1,1-diphenyl-2-picryl-hydrazil (DPPH), Nitric Oxide (NO), and Hydrogen Peroxide (H₂O₂) scavenging activities. In addition, the antihemolytic and antimicrobial activities were estimated and the phenolic compounds (phenolic acids and flavonoids) were evaluated by HPLC. Among the ten species, extract of  C. ‎tomentosum and S. aquifolium has recorded the highest value of ‎TPC (18.83±1.62 and 18.51±2.22 mg equivalent/g dry extract, ‎respectively) and the TFC was 3.77±0.41 and 3.45±0.41 mg equivalent/g ‎dry extract, respectively. Also, the two species showed significantly ‎greater radical scavenging ability in DPPH radicals (IC50 5.41 and 5.51 ‎mg/ml,  respectively), NO (IC50 5.31 and 8.24 mg/ml,  respectively) and H₂O₂ (IC50 0.425 and 0.332 ‎mg/ml,  respectively).‎ Interestingly, the crude extract of C. tomentosum ‎and S. aquifolium‏ ‏showed the lowest hemolytic activities however, they showed strong antimicrobial activity. Conclusively, this study highlights the interesting candidates for the pharmaceutical and medicinal applications owing to their antioxidant and antimicrobial activities, which may lay the foundation for developing a new therapeutic intervention from seaweeds.