The Democratic Party of Illinois is a political party and affiliate of the United States Democratic Party in Illinois. This party currently holds a majority in both the Illinois Senate and Illinois House of Representatives. The Governor of Illinois, Rod Blagojevich, and both of Illinois' United States Senators, Barack Obama and Dick Durbin, are members of this party. Michael Madigan is the party's current Chairman.

The Chicago Democratic Machine is a well known example of machine politics.