Abstract Lighting is one of the basic pillars of life, and Islamic civilization was the best evidence of the development of natural lighting methods. Today's religious buildings have largely neglected the element of natural lighting, and have been replaced by a huge amount of expensive artificial lighting; even in broad daylight. Therefore, natural lighting must be utilized as a basic element in mosque architecture. This research examines the impact of natural lighting on religious buildings, and explores how natural lighting affects the experience of worshippers and visitors. The study discusses how natural lighting affects the atmosphere and functions of religious spaces, and what design criteria can increase natural lighting in religious buildings in Iraq. The study uses a qualitative approach that combines architectural analysis and empirical observations. The methodology and tools are the architectural analysis of existing religious buildings and the evaluation of design features (windows, domes...) that facilitate natural light. The study concluded that natural lighting affects the spiritual and aesthetic aspects of religious buildings. Architectural elements such as windows, courtyards, and domes play a role in achieving perfect lighting.