One of the core roles of a practising geotechnical engineer is to analyse and design foundations. This textbook for advanced undergraduates and graduate students covers the analysis, design and construction of shallow and deep foundations and retaining structures as well as the stability analysis and mitigation of slopes. It progressively introduces critical state soil mechanics and plasticity theories such as plastic limit analysis and cavity expansion theories before leading into the theories of foundation, lateral earth pressure and slope stability analysis. On the engineering side, the book introduces construction and testing methods used in current practice. Throughout it emphasizes the connection between theory and practice. It prepares readers for the more sophisticated non-linear elastic-plastic analysis in foundation engineering which is commonly used in engineering practice, and serves too as a reference book for practising engineers.