William Jay Smith (September 24, 1823 – November 29, 1913) was an American politician and a member of the United States House of Representatives for Tennessee's 8th congressional district.

Smith was born in Birmingham, England on September 24, 1823, and immigrated to the United States and settled in Orange County, New York.

Despite labeling himself a Unionist and being a Union Army officer, Smith gained a reputation for seizing everything from furniture to mules and slaves and sending them back to his own plantation to enrich himself.

His misdeeds remained largely unknown until the discovery of Breckenridge's diary in 2012 and the subsequent publication of In The Shadow of the Devil: William K.M.

Smith died in Memphis, on November 29, 1913 (age 90 years, 66 days), while walking down the street, due to sudden heart failure.