Developed from a course taught to senior undergraduates, this book provides a unified introduction to Fourier analysis and special functions based on the Sturm-Liouville theory in L². The treatment relies heavily on the convergence properties of sequences and series of numbers as well as on function. The text's presentation follows a clear, rigorous mathematical style that is highly readable and easy to follow. Coverage begins with a description of the mathematical tools for building the Sturm-Liouville theory. Next, the author develops the theory and then presents the fruits of the theory. In addition, the book covers Fourier transforms and extends Fourier series to non-periodic functions. The many worked examples and exercises with solutions make the book suitable for self-study as well as accessible to undergraduate students in mathematics, physics, engineering, and related fields.