William Thomas Harris III (born September 22, 1940) is an American writer, best known for a series of suspense novels about his most famous character, Hannibal Lecter. The majority of his works have been adapted into films and television, the most notable being The Silence of the Lambs, which became only the third film in Academy Awards history to sweep the Oscars in major categories.

His notable works are Red Dragon (1981), The Silence of the Lambs (1988), Hannibal (1999), Hannibal Rising (2006), Black Sunday (1975), and Cari Mora (2019)

Fellow novelist Stephen King remarked that if writing is sometimes tedious for other authors, to Harris it is like "writhing on the floor in agonies of frustration", because for Harris, "the very act of writing is a kind of torment". Novelist John Dunning said of Harris, "All he is is a talent of the first rank." In 2019, he elaborated on his process, as well as the difficulty, describing it as "passive [...], sometimes you really have to shove and grunt and sweat. Some days you go to your office and you're the only one who shows up, none of the characters show up, and you sit there by yourself, feeling like an idiot. And some days everybody shows up ready to work. You have to show up at your office every day. If an idea comes by, you want to be there to get it in."