William Frederick "Heinie" Heitmuller (May 25, 1883 – October 8, 1912) was an American left fielder in Major League Baseball.

He was born in San Francisco, California, and died at age 29 in Los Angeles.

After attending the University of California, Berkeley, Heitmuller played for several years in the Pacific Coast League.

Overall, Heitmuller played in 95 major league games, 89 as an outfielder and 69 in left field.

He was the PCL's leading hitter with a .335 batting average, a .471 slugging percentage and a career-high 15 home runs when he contracted typhoid fever late in the 1912 season.