William Guy Mallory (May 30, 1935 – May 25, 2018) was an American college football player and coach. He served as the head football coach at Miami University in Oxford, Ohio from 1969 to 1973, the University of Colorado at Boulder from 1974 to 1978, Northern Illinois University from 1980 to 1983, and Indiana University Bloomington from 1984 to 1996, compiling a career head coaching record of 168–129–4.

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. Before taking over the head coaching reins at Indiana in 1984, Mallory coached three other schools to national prominence. 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. In 1987, Mallory became the first coach to be awarded back-to-back Big Ten coach-of-the-year honors. While at Indiana, Mallory led the Hoosiers to six bowl games including victories in the 1988 Liberty Bowl, and the 1991 Copper Bowl. He also led IU to a top 20 ranking in 1987 and 1988.

Early in his coaching career, Mallory served as assistant to Woody Hayes at Ohio State University, Carmen Cozza at Yale University and Doyt Perry at Bowling Green State University.

Mallory is a member of Miami University's Cradle of Coaches. He is also a member of the Athletic Halls of Fame at Miami University and Indiana University, the Mid-American Conference,^[1] the Indiana Football Hall of Fame and the Phi Kappa Tau Hall of Fame.

Mallory was the 15th head college football coach for the Northern Illinois University Huskies located in DeKalb, Illinois and he held that position for four seasons, from 1980 until 1983. He coached the Huskies to victory in the 1983 California Bowl, the school's first major bowl game appearance. Mallory's career coaching record at Northern Illinois was 25 wins, 19 losses, and 0 ties. This ranks him sixth at Northern Illinois in total wins and seventh at NIU in winning percentage.^[2]

Mallory died in Bloomington, Indiana, on May 25, 2018, just five days before his 83rd birthday and less than three weeks before his 60th wedding anniversary with his wife Ellie, following brain surgery from a fall on May 22.^[3]