Due to innovations in construction technology and increasing land prices, the number of high-rise buildings has increased dramatically. These buildings are known for their high energy consumption, which caused by many factors including architectural and operational factors. Heating, ventilation, and air conditioning systems (HVAC) is one of the operational factors which led to intensive energy consumption. In the light of the global energy crises along with advanced simulation tools, architects have been motivated to improve the energy performance of buildings through controlling design parameters. This research discusses the impact of Window to Wall Ratio (WWR), as an important parameter of building's envelope design, on the total annual energy consumption of high-rise office buildings. It aims to determine the optimal WWR in terms of energy performance across the Egyptian different climatic regions. Many related previous works, in different climates, have been reviewed in order to theoretically extract the variables employed in this work. According to the review, nine WWR ranging from 10% to 90% in two shapes, square and rectangular, were adopted to be modeled using the DesignBuilder simulation tool. The proposed models were simulated within seven Egyptian cities (Alexandria, Cairo, Minya, Assiut, Hurghada, El-Kharga, and Aswan) representing the seven classified climatic regions in Egypt. The findings revealed that the optimal WWR is (20%) for the rectangular shape and (20-30%) for the square shape across all Egyptian cities. The energy conservation ranged between (53.3- 60.8%) and (41-49%) in the rectangular and square models, respectively, in comparison to the worst case