Current delegation

Illinois was admitted to the Union on December 3, 1818, and has been represented in the United States Senate by 47 senators. Senators from Illinois are elected to Class 2 and Class 3.

The Senate twice refused to seat Frank L. Smith, in December 1926 for an appointed term and in March 1927 for an elected one, due to corruption, but he is included in this list because Smith and the Governor considered him to be a senator for approximately two years.

Of the eight African Americans ever to sit in the U.S. Senate since Reconstruction, three have held Illinois's Class 3 seat, including Barack Obama who went on to become the president of the United States. This makes Illinois the state with the most African-American senators. Illinois's current U.S. senators are Democrats Dick Durbin (serving since 1997) and Tammy Duckworth (serving since 2017).

List of senators