The original goal in writing this book was to introduce the reader to the tools of combinatorics from an applied point of view. This third edition of Applied Combinatorics was substantially rewritten. There are many new exercises. Additionally, references throughout the book have been updated both in terms of new editions of previously referenced works, as well as with references to recently published books and articles. As the first edition appeared decades prior, the diction in the exposition has been updated and is more contemporary.