The first edition of Hardy's Integration of Functions of a Single Variable was published in 1905, with this 1916 second edition being reprinted up until 1966. Now this digital reprint of the second edition will allow the twenty-first-century reader a fresh exploration of the text. Hardy's chapters provide a comprehensive review of elementary functions and their integration, the integration of algebraic functions and Laplace's principle, and the integration of transcendental functions. The text is also saturated with explanatory notes and usable examples centred around the elementary problem of indefinite integration and its solutions. Appendices contain useful bibliographic references and a workable demonstration of Abel's proof, rewritten specifically for the second edition. This innovative tract will continue to be of interest to all mathematicians specialising in the theory of integration and its historical development.