Illinois's 3rd congressional district

Illinois's 3rd congressional district includes parts of Cook County and DuPage County, and has been represented by Democrat Delia Ramirez since January 3, 2023. Prior to being drastically reconfigured to a different region in 2023, when it was created largely out of portions from the 4th and 6th districts, the district was represented by Marie Newman from 2021 to 2023, Dan Lipinski from 2005 to 2021, and by Lipinski's father Bill from 1983 to 2005.

The district includes portions of the Northwest Side of the city of Chicago as well as the city's western suburbs stretching across DuPage County to its western edge, and covers 124.5 square miles (322 km²), making it one of the 50 smallest districts in the U.S., although there are five smaller districts in Illinois. It is adjacent to the 1st district to the east and south, the 4th district to the north, and the 11th district to the west, and also borders the 6th and 7th districts at its northwestern and northeastern corners, respectively. The district was created following the 1830 census and came into being in 1833, five months before Chicago was organized as a town; it initially included northern and western Illinois before representing areas of east-central and northwestern Illinois from 1843 to 1873. The district has included part of Chicago since 1873, and part of the city's southwest side from 1895 to 2023; the district has been primarily suburban since 1973.