An accessible yet rigorous mathematical introduction, A Theoretical Introduction to Numerical Analysis provides a pedagogical account of the fundamentals of numerical analysis. Using numerical methods from real analysis, linear algebra, and differential equations, the authors explain basic concepts, such as error, discretization, efficiency, complexity, numerical stability, consistency, and convergence. The text also addresses more complex topics like intrinsic error limits and the smoothness of approximated functions in the context of Chebyshev interpolation, Gaussian quadratures, and spectral methods for differential equations. The authors often delineate various techniques through exercises that require further theoretical study or computer implementation.