John Edward Charles O'Sullivan Addicks (November 21, 1841 – August 7, 1919) was an American industrialist and capitalist who used his wealth from financing and building gas works to wage four unsuccessful campaigns for a United States Senate seat in Delaware. His struggle with Henry A. du Pont for control of the state government led to Delaware having both of its Senate seats vacant for a time and was one of the factors that led to election reform and the Seventeenth Amendment to the United States Constitution in 1913.