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- Kyung Lah, Tokyo-based international correspondent for CNN
- Ray LaHood, Politician (Republican), former Member of the U.S. and Illinois House of Representatives, current U.S. Secretary of Transportation
- Gene Lamont, former MLB catcher, former MLB manager, current third base coach for the Detroit Tigers
- James Landis, noted power engineer
- Eric Lane, actor
- Norm Larsen, industrial chemist, inventor of WD-40
- René-Robert Cavelier, Sieur de La Salle, explorer
- Carol Lawrence, actress
- Natasha Leggero, stand-up comedienne, actress, judge on Last Comic Standing
- John D. LeMay, actor, Friday the 13th: The Series
- Harry Lennix, actor, Dollhouse, Commander in Chief, The Matrix Reloaded, The Matrix Revolutions
- Thomas Lennon, actor, comedian, Reno 911!, The State, Viva Variety
- Rick Lenz, actor, Hec Ramsey
- Donald Leslie, inventor of the Leslie speaker
- Brian Levant, film director, The Flintstones
- Charles Levin, actor, Alice, Capital News
- Greg Lewis, wide receiver for the Minnesota Vikings
- Jeffrey Lieber, TV writer and producer, Lost, Miami Medical
- DeAndre Liggins, shooting guard for the Orlando Magic
- Abraham Lincoln, 16th President of the United States, member of Congress
- Mary Todd Lincoln, Abraham Lincoln's wife
- Robert Todd Lincoln, attorney, U.S. Ambassador to the United Kingdom, U.S. Secretary of War, President of the Pullman Company, Abraham Lincoln's son
- Charles Magnus Lindgren, Shipping Executive
- John R. Lindgren, Banking Executive, son of Charles M. Lindgren
- Vachel Lindsay, poet
- Shaun Livingston, player for the Milwaukee Bucks
- Nils Lofgren, rock music recording artist, songwriter, and multi-instrumentalist
- John A. Logan, politician (Democrat and Republican), U.S. Civil War General, member of the U.S. and Illinois House of Representatives, U.S. Senator
- Ramón E. López, space physicist
- Tony Lovato, musician, member of the band Mest
- Frank Orren Lowden, politician (Republican), member of the U.S. House of Representatives and Illinois Governor
- Jane Lynch, actress and comedienne; The 40-Year-Old Virgin, Talladega Nights, Alvin and the Chipmunks
- Ginger Lynn, porn actress
Read more about this topic: List Of People From Illinois