William Grant Mills (August 15, 1877 – March 14, 1933), nicknamed Wee Willie, was a professional baseball pitcher.

Mills earned his nickname due to his stature; he stood only 5'7" and weighed about 150 lbs.

Mills played two years of college baseball at Oneonta Normal School.

He would post a 47-26 record with Utica over two seasons, leading the club to the 1900 New York State League championship.

This biographical article relating to an American baseball pitcher born in the 1870s is a stub.