William Aldrich (January 19 1820 – December 3 1885) was a United States Representative from the state of Illinois. He was born in Greenfield Center in the Town of Greenfield in New York. He attended local schools and taught school himself.

Aldrich moved to Michigan and then to Wisconsin where he worked as a shopkeeper and manufacturer. He moved to Chicago, Illinois in 1861 and opened another shop.

He served as congressman from 1877 to 1883 after having earlier served in the Wisconsin State Assembly.

Aldrich died in Fond du Lac, Wisconsin. He is buried in Rosehill Cemetery in Chicago.