The 3rd Illinois General Assembly, consisting of the Illinois Senate and the Illinois House of Representatives, met from December 2, 1822, to February 18, 1823, during the first two years of Edward Coles' governorship, at The Vandalia State House.

The apportionment of seats in the House of Representatives was based on the provisions of the First Illinois Constitution.

Political parties were not established in the State at the time.

Senators and Representatives were both allotted to counties roughly by population and elected at-large within their districts.

Greene and White counties shared one senator.