William Horace Frankhauser (March 5, 1863 – May 9, 1921) was a politician from the U.S. state of Michigan. Frankhauser was born in Wood County, Ohio and moved with his parents to Monroe, Michigan, in 1875. He attended the public schools, Michigan State Normal School (now Eastern Michigan University at Ypsilanti, Michigan, and Oberlin College, Oberlin, Ohio. He was a school teacher for several years, studied law and was admitted to the bar in 1891. He commenced practice in Hillsdale, Michigan and became city attorney and prosecutor of Hillsdale County, 1896-1903.