Charles H. Percy Republican Paul Simon Democratic The 1984 United States Senate election in Illinois took place on November 6, 1984.

Senator Percy was opposed by Democratic nominee Paul Simon, who was a United States Congressman from Illinois's 22nd congressional district.

Simon also won most counties in southwestern Illinois, a traditionally Democratic region.

[3] Percy led early on and well into the night, but as Cook County began to count all of its votes, Simon pulled ahead.

Simon was later succeeded by Dick Durbin, a close friend and fellow Democrat.