Abstarct: Light, as one of the fundamental elements in architecture, plays an irreplaceable role in shaping and experiencing artificial spaces. Since ancient times, architects have always used light to create meaningful spaces and improve the quality of life. In modern times, architects such as Le Corbusier called light the "material of architecture" and emphasized its importance in the human experience. Contemporary research shows that natural light can help improve physical and mental health, reduce energy consumption, and improve the quality of living spaces. However, in today's world, population growth and excessive urban development have caused the importance of light in housing design to be given more attention. This research was conducted with the aim of investigating the effect of natural light on the sustainability and quality improvement of residential complex design. The research data was collected using a library method and included an analysis of previous studies, a review of the theories of prominent architects, and an evaluation of new lighting design methods. This research emphasizes the relationship between natural light and the quality of residential spaces, which, in addition to meeting aesthetic needs, also pursues environmental sustainability and energy savings. The design of this research was carried out in the city of Mashhad, and the presence of natural light in a residential complex was analyzed and tested in Mashhad. The results of the research show that natural light plays a key role in the sustainability of residential spaces. Proper design of building orientation, the use of technologies such as light shelf windows and louver systems, and the selection of appropriate materials can lead to better guidance and distribution of light, reduce energy consumption, and create beautiful and efficient spaces. Also, natural light has a positive effect on the physical and mental health of individuals and can help reduce stress, improve mood, and increase satisfaction with the living environment. This research attempts to provide a platform for improving the quality of housing design using natural light by providing innovative solutions and helping to improve the quality of life and environmental sustainability.