The article explores the concept of sustainable interior design as an architectural approach that aims to achieve a balance between the aesthetic, functional, and environmental aspects of interior spaces, with a particular focus on rationalizing energy consumption and improving building performance. Interior design is no longer limited to furniture arrangement and the selection of colours and materials; it has become an essential factor in reducing environmental impact through the adoption of design solutions that consider natural resources and minimize energy waste. The article highlights the importance of utilizing natural lighting by carefully studying the locations of windows and openings and orienting interior spaces to maximize the benefits of sunlight, thereby reducing the need for artificial lighting during daylight hours. It also examines the role of natural ventilation in improving indoor air quality and reducing dependence on air-conditioning systems, in addition to the importance of selecting environmentally friendly building and finishing materials with thermal insulation properties that limit heat gain or loss. These measures help maintain comfortable indoor temperatures and reduce energy consumption. Furthermore, the article discusses the impact of selecting colours, materials, and furniture on enhancing energy efficiency. Light colours and reflective surfaces can improve the distribution of light within spaces, while sustainable and recycled materials help reduce the depletion of natural resources and minimize waste. It also addresses the role of smart technologies, such as lighting and air-conditioning control systems and motion sensors, in managing energy consumption according to users’ needs and the intended use of each space. The article emphasizes that sustainable interior design represents an environmental and human responsibility that extends beyond the aesthetic appearance of a building. It contributes to creating healthy and comfortable indoor environments, reducing operational costs, and preserving natural resources. It also highlights the important role of interior designers in making informed decisions that combine innovation, beauty, and environmental efficiency, ultimately contributing to more sustainable buildings capable of responding to present demands and the needs of future generations. Al-Mustaqbal University – Ranked First Among Private Universities in Iraq.