William McKinnon Fetzer (June 24, 1884 – May 3, 1959) was an American football, basketball, and baseball coach. He served as the head football coach at Davidson College (1915–1918), North Carolina State University (1919–1920), and the University of North Carolina at Chapel Hill (1921–1925), compiling a career college football record of 61–28–7. His brother, Bob Fetzer, served as co-head football coach at the University of North Carolina and later became the first and longest serving Athletics Director for the university. Fetzer also was the head basketball coach at Davidson for two seasons, from 1916 to 1918, tallying a mark of 18–11. In addition, he coached baseball at Davidson (1915–1919), NC State (1920), and North Carolina (1921–1925), amassing a career college baseball record of 128–75–5.

Fetzer was also a professional baseball player. He made his Major League Baseball (MLB) debut on September 4, 1906 as a pinch hitter for the Philadelphia Athletics. In his lone at bat Fetzer failed to record a hit. This would be his only major league game, although he continued to play in the minor leagues, primarily as an outfielder, until 1910. He threw with his left hand and hit with his right. Prior to his professional career, Fetzer played collegiately at Davidson College.