The 18th congressional district of Illinois covered central and western Illinois, including all of Jacksonville and Quincy and parts of Bloomington, Peoria, and Springfield. It covered much of the territory represented by Abraham Lincoln during his single term in the House.

It was last represented by Republican Darin LaHood, who took office in September 2015 following a special election.^[1]

Republican Aaron Schock previously represented the district from January 2009 until his resignation in March 2015.^[2] Darin LaHood is the son of Schock's predecessor, Ray LaHood, and was reelected in 2016, 2018, and 2020.

From 1949 to 2015, the district was always represented by an attendee or graduate of Bradley University. Due to reapportionment after the 2020 U.S. census, the 18th district was eliminated ahead of the 2022 elections.

The district covered parts of McLean, Peoria, Sangamon, Stark and Tazewell counties, and all of Adams, Brown, Cass, Hancock, Logan, Marshall, Mason, McDonough, Menard, Morgan, Pike, Schuyler, Scott and Woodford counties, as of the 2011 redistricting which followed the 2010 census. All or parts of Bloomington, Chatham, Jacksonville, Lincoln, Macomb, Morton, Normal, Peoria, Quincy and Springfield are included.^[3] The representatives for these districts were elected in the 2012 primary and general elections, and the boundaries became effective on January 5, 2013.

* Write-in and minor candidate notes: In 1994, write-ins received 955 votes. In 1998, write-ins received 2 votes. In 2008, Green Party candidate Sheldon Schafer received 9,857 votes. In 2010, Schafer received 11,256 votes.

• Illinois's congressional districts
• List of United States congressional districts