Acute toxicity bioassays are essential tools for assessing the ecotoxicological risks of chemical pollutants in aquatic environments. Among these, the Artemia nauplii immobilization test offers a rapid, cost-effective, and standardized approach for screening toxic substances. This study evaluated the acute toxicity of four heavy metal sulfates (copper, zinc, cadmium, and lead) using Artemia salina nauplii, with potassium dichromate as the reference toxicant. Artemia cysts were hatched under optimized conditions, including controlled salinity (35 ppt), pH (8.0-8.5), temperature (28°C), and continuous aeration to ensure maximum hatching success and larval viability. Toxicity tests were conducted using stage II nauplii, selected for their enhanced sensitivity to environmental contaminants, exposed to serial dilutions of each heavy metal for 24 hours following standardized protocols. Mortality rates were recorded to determine acute toxicity parameters, including 24 h LC₅₀ and LC₁₀₀ values. The results indicated that copper was the most toxic heavy metal tested, followed by lead, cadmium, and zinc, with the toxicity ranking as follows: Cu > Pb > Cd > Zn. The LC₅₀ values demonstrated that Artemia nauplii exhibited differential sensitivity to heavy metals, with copper and lead showing significantly higher toxicity compared to cadmium and zinc. Despite this differential toxicity, Artemia nauplii demonstrated considerable tolerance to heavy metal exposure across all the tested concentrations. These findings contribute to the classification and comparative assessment of heavy metal toxicity in aquatic invertebrates and underscore the utility of the Artemia bioassay as a first-tier screening tool for environmental risk assessment.