Al-Razzaza Lake is one of the most important water resources in Iraq, holding significant economic and environmental value for the country. The lake is now undergoing significant ecological changes and experiencing water level declines, primarily driven by increased evaporation due to climate change and reduced inflow from the Euphrates River. It is, therefore, important to monitor the changes affecting the lake using remote sensing and geographic information systems (GIS). This study aims to assess environmental changes in Al-Razzaza Lake by analyzing Landsat 4-5 images for 2004 and Landsat 8-9 images for 2014 and 2024. Climate data were obtained from the NASA Energy website (2004 and 2014) and the Al-Razzaza station of the Ministry of Agriculture (2024). Supervised classification using the Maximum Likelihood method and the Normalized Difference Water Index (NDWI) was applied to classify the study area into water, soil, and vegetation. The classification achieved overall accuracies of 94%, 97%, and 98% for 2004, 2014, and 2024, respectively. The results indicated that the water surface area declined significantly from 549.22 km² in 2004 to 189.77 km² in 2024, accompanied by an expansion in the soil area and a reduction in vegetation cover. A strong inverse correlation (r = -0.98) was observed between high temperatures and declining water surface areas, while a positive correlation (r = 0.98) was found between rainfall and water surface areas. The study features the alarming degradation of Al-Razzaza Lake and the urgent need for continuous monitoring and adaptive water resource management strategies.