Algae are emerging as a promising source for biodiesel production, with the potential to completely replace fossil fuels. Since two-thirds of the Earth's surface is covered by water, algae present a renewable option with significant global potential to meet future energy needs. The current study investigated biodiesel production from Cladophora sp. via direct transesterification. Oil was extracted from the algae to determine the oil yield. The study also explored algae pretreatment methods, including ultrasound and heat treatment (autoclaving), to enhance oil extraction. The results demonstrated that the ultrasound method was superior. The percentage of extracted oil was 26%, representing a 3.5% increase compared to direct extraction without pretreatment, which yielded 22.5%. The direct transesterification process was performed using an algae-to-methanol ratio of 8:1 (w/w). Concentrated sulfuric acid (H₂SO₄) at a 3% (w/w) ratio was used as a catalyst. The mixture was heated for 60 minutes at 50°C. The resulting biodiesel was characterized using GC-MS and FTIR. The biodiesel yield was calculated at 78%. Key properties, including density, viscosity, pour point, cloud point, and acidity value, were determined and compared with standard diesel properties according to ASTM specifications. The results indicated that Cladophora sp. is a valuable source for biodiesel production, offering a reasonable yield of biodiesel with properties that conform to ASTM standards.