William Guy Mallory (May 30, 1935 – May 25, 2018) was an American college football player and coach.

Mallory played football at Miami University for coaches Ara Parseghian and John Pont.

Mallory is the Indiana Hoosiers' winningest football coach, having compiled a 69–77–3 record.

While compiling a 168–129–4 career record, Mallory became one of only a handful of coaches in history to guide three different programs to top 20 finishes in national polls.

Mallory's career coaching record at Northern Illinois was 25 wins, 19 losses, and 0 ties.