The 85 Ways to Tie a Tie is a book by Thomas Fink and Yong Mao about the history of the knotted neckcloth, the modern necktie, and how to tie both. It is based on two mathematics papers published by the authors in "Nature" and "Physica A" while they were research fellows at Cambridge University’s Cavendish Laboratory. The authors prove that, assuming both the tie and the wearer to be of typical size, there are exactly 85 ways of tying a necktie using the conventional method of wrapping the wide end of the tie around the narrow end. They describe each and highlight those that they determine to be historically notable or aesthetically pleasing.