William Van Amberg Sullivan (December 18, 1857 – March 21, 1918) was a United States representative and Senator from Mississippi.

[1] He graduated from Vanderbilt University, in Nashville, Tennessee, in 1875, was admitted to the bar that year, and commenced practice in Austin.

He moved to Oxford in 1877, was a member of the board of city aldermen, and was elected as a Democrat to the Fifty-fifth Congress and served from March 4, 1897, to May 31, 1898, when he resigned, having been appointed Senator.

He was appointed and subsequently elected to the U.S. Senate to fill the vacancy caused by the death of Edward C. Walthall and served from May 31, 1898, to March 3, 1901; he was not a candidate for reelection.

On September 8, 1908, Sullivan led a lynch mob which murdered a black man named Nelse Patton, who had been accused of killing a white woman.