Book excerpt: X-ray line profile analysis is an effective and non-destructive method for the characterization of the microstructure in crystalline materials. Supporting research in the area of x-ray line profile analysis is necessary in promoting further developments in this field. X-Ray Line Profile Analysis in Materials Science aims to synthesize the existing knowledge of the theory, methodology, and applications of x-ray line profile analysis in real-world settings. This publication presents both the theoretical background and practical implementation of x-ray line profile analysis and serves as a reference source for engineers in various disciplines as well as scholars and upper-level students.