X-ray photoelectron spectroscopy (XPS) is a surface susceptible quantitative spectroscopic technique based on the photoelectric effect, used to identify the elements that may be present in a material or layer at the surface, as well as to determine their chemical state, the respective electronic structure and the density of electronic states in the different materials. XPS is the most commonly used measurement technique for analyzing various materials, showing not only which elements are present, but also the other elemental materials associated with the material. This characterization technique can be used to create line profiles of elemental composition on the surface or in conjunction with ion beam etching for depth profiling. It is often used to study chemical processes that occur in the material in its purest form and in the state in which it was obtained, such as scraping, exposure to heat, reactive gasses or solutions, ultraviolet light, and ion implantation. In this regard, the present chapter would discuss the construction, working principle, and application of the XPS technique in detail.