Emily Cox is a US puzzle writer. She and her partner, Henry Rathvon, 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, Sunday crosswords for The Boston Globe, cryptic crosswords for Canada's National Post, and puzzles for the US Airways in-flight magazine, Attache.

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