llinois is a 2005 concept album by American indie folk songwriter Sufjan Stevens (pictured). His fifth studio album, Illinois is Stevens' second based on a U.S. state—part of a planned series of fifty that began with the 2003 album

Michigan and that Stevens has since acknowledged was a gag. Stevens recorded and produced the album at multiple venues in New York City using low-fidelity studio equipment and a variety of instruments between late 2004 and early 2005. The artwork and lyrics explore the history, culture, art, and geography of the state; Stevens developed them after analyzing criminal, literary, and historical documents. This release also continued a trend in Stevens' career of referencing his Christian faith in his lyrics. Following a July 4, 2005, release date, Stevens promoted Illinois with a world tour. Critics praised the album for its well-written lyrics and complex orchestrations. Illinois was named the best-reviewed album of 2005 by review aggregator Metacritic and was included on several reviewers' "best of the decade" lists—including those of Paste, NPR, and Rolling Stone. The album was Stevens' first to place on the Billboard 200.