Henry Rathvon is a puzzle writer. He and his partner, Emily Cox, write The Puzzler, a cryptic crossword featured each month in the magazine The Atlantic Monthly for almost 30 years until recently. (Since March 2006, the Puzzler has been published solely online at The Atlantic's website, available only to the magazine's subscribers.) They also create acrostic puzzles for the New York Times, cryptic crosswords for Canada's National Post, puzzles for the US Airways in-flight magazine, Attache, and (with Henry Hook) Sunday crosswords for the Boston Globe.

In 2005, Rathvon's play Trapezium, a comedy in iambic pentameter, was produced by the Orlando-UCF Shakespeare Festival.

Henry Rathvon and Emily Cox are members of the National Puzzlers' League under the joint "nom" "Hex" (a blend of his first name and her last name).