This comprehensive course offers a complete introduction to geotechnical engineering and retaining wall design. Students will learn about the essential properties of soil and rock and how they interact with structures. The course emphasizes the importance of geotechnical engineering in ensuring the safety and sustainability of structures, as well as the crucial role of retaining walls in preventing erosion, providing stability to structures, and creating level surfaces on sloping ground. The course delves into the basic principles and terminology of retaining walls, covering everything from the forces on retaining walls to the different types of retaining walls, including gravity retaining walls, semi-gravity retaining walls, cantilever retaining walls, counterfort retaining walls, anchored retaining walls, and mechanically stabilized earth retaining walls. Students will gain an understanding of the categories of lateral earth pressure, including at-rest condition, active pressure, and passive pressure, as well as the design process for retaining walls. In addition to learning about retaining wall design and analysis, students will also gain knowledge about the materials used in retaining wall construction, the importance of thorough investigation to ensure the durability and serviceability of retaining walls, and the calculation of lateral earth pressure coefficients using the Rankine earth pressure theory and the KULOM active earth pressure theory. The course covers the importance of designing structures to withstand natural disasters, such as earthquakes and floods, and the concept of building lifespan, codes that provide the expected lifespan of structures, and the importance of designing structures for a certain period of time. Students will gain insights into case studies and examples of retaining wall failures to highlight the significance of proper design and investigation and the importance of rehabilitation versus replacement of structures. Upon completion of this course, students will be equipped with the knowledge and skills to design and analyze retaining walls that are durable, safe, and reliable. They will also have a thorough understanding of geotechnical engineering, the forces on retaining walls, the different types of retaining walls, and the categories of lateral earth pressure, enabling them to collaborate effectively with geotechnical engineers to design stable and safe structures with effective retaining walls.