Since Illinois became a U.S. state in 1818, it has sent congressional delegations to the United States Senate and United States House of Representatives. Each state elects two senators to serve for six years, and members of the House to two-year terms. Before becoming a state, the Illinois Territory elected a non-voting delegate at-large to Congress from 1812 to 1818.
These are tables of congressional delegations from Illinois to the United States Senate and the United States House of Representatives.