The essential nutrients for a well-balanced feed supplement, such as polysaccharides, fatty acids, amino acids, antioxidants, vitamins, and minerals are often abundant in marine macroalgae. The recent study examined and compared the phytochemical, antibacterial, and antioxidant properties of Ulva lactuca and Ulva fasciata Lin (Chlorophyceae). Different extracts (acetone, benzene, methanol, and aqueous) at various doses (100, 200, 300, 400, and 500 ppm) were used to study the larvicidal effects of Ulva lactuca Lin (Chlorophyceae) against Anopheles stephensi. The study used early 4th instar larvae of Anopheles stephensi and followed the WHO procedure to determine the treated larvae's fatal concentrations (LC50 and LC90). The observed mortality was recorded 24 to 48 hours after treatment. The acetone extracts of Ulva lactuca and Ulva fasciata contained phenolic components, tannins, and terpenoids. The results showed that each extract had different levels of larvicidal efficacy against Anopheles stephensi. Ulva lactuca methanol extract exhibited exceptional larvicidal action against Anopheles stephensi. Ulva lactuca's aqueous extract had the lowest larval mortality compared to acetone, benzene, methanol, and ethanol extracts. This study found Ulva lactuca's methanolic extract is effective against Anopheles stephensi larvae, making it an eco-friendly mosquito control option.