Separation referendums in Illinois

Beginning in 2020, a number of counties of Illinois have held referendums relating to the separation of Cook County, and more specifically its city of Chicago, from the rest of Illinois. This might be achieved by splitting Chicago and some nearby areas off as a new state, separating themselves from Illinois to form a new state, or separating from Illinois and joining a neighboring state. The counties that have held these referendums tend to be thinly populated rural areas, mostly in the state's southeast. Advocates state that the dominance of Cook County in state politics means that such areas are ignored. These referendums are not legally binding, and a division of the state is ultimately unlikely. The referendums and related legislation have thus sometimes been used to raise awareness of other political issues, and make political statements.

The modern politics of Illinois is dominated by Cook County, as it contains 40% of the state's population. This has made evident a strong urban–rural political divide, with the Democratic Party-leaning Cook County residents holding differing views on a number of issues to the more Republican Party-leaning rural residents. The state also has a long history of regional cultural differences, especially between Chicago and the rest of Illinois, which is referred to as "downstate".

While proposals to divide Illinois are not new, the current series of "separation referendums" were prompted by the close 2010 Illinois gubernatorial election, in which the winner, Pat Quinn, won only four counties, despite winning a plurality of overall votes. A bill to separate Chicago from the rest of Illinois was subsequently presented to the Illinois House of Representatives, but did not progress. An organization named "New Illinois" was formed in 2018 to advocate for separation. In 2019 a new resolution for separation was introduced to the House, which also did not proceed to a vote.

The first referendums on the county level occurred in March 2020, occurring alongside state primary elections. This initial three was soon followed by 20 more in November, which were held alongside the 2020 Illinois elections. One county held a referendum in 2021, while the 2022 Illinois elections saw referendums held in two more counties and two townships of a third. This third county and six others held referendums alongside the 2024 Illinois elections.