This textbook summarizes various studies and significant materials on data analytics in spectroscopy. Its rigorous mathematical basis, in-depth description, and numerous examples of applications in chemistry and physics make this book valuable for theorists, practitioners, and students specializing in data processing in spectroscopy, chemometrics, and analytical chemistry.The bibliography briefly describes hundreds of data analytics applications for solving spectroscopic tasks in industrial and research laboratories. This book differs from existing brief reviews and articles on this topic in that it forms, for the first time, the big picture of all kinds of data analytics methods in spectroscopy. The book also provides quickly reproducible computer calculations to illustrate its significant theoretical statements. As such, it can also serve as a practical guide to lecturers in data analytics in the broad field of spectroscopy, including chemometrics and analytical chemistry.