K
- Mike Kafka, quarterback for the Philadelphia Eagles
- Harry Kalas (1936–2009), sportscaster, play-by-play for the Philadelphia Phillies
- Maria Kanellis, WWE Diva
- Henry Kaplan, radiologist who pioneered in radiation therapy and radiobiology
- Leon Kass, physician, scientist, educator, public intellectual
- Leslie Keeley, physician and founder of the Keeley Institute for addiction treatment
- Florence Kelley, social reformer, labor-rights advocate and founder of the National Consumers' League
- Robert Keohane, co-founder of the neoliberalism school of thought
- Johnny Kerr, NBA player and coach, color commentator for the Chicago Bulls
- Brian Kerwin, actor, One Life to Live, Beggars and Choosers, The Misadventures of Sheriff Lobo
- T'Keyah Crystal Keymáh, actress, That's So Raven, Cosby, In Living Color
- Fazlur Khan (1929–1982), structural engineer
- Richard Kiley (1922–1999), actor, A Year in the Life, Kraft Television Theatre, Phenomenon
- Sam Kinison (1953–1992), stand-up comedian, actor
- Terry Kinney, actor, Oz, The Unusuals, The Firm
- John Kinzie, Chicago settler
- Jason Kipnis, second baseman for the Cleveland Indians
- Chris Klein, actor, American Pie film series
- Frank Knox, newspaper publisher/owner and Secretary of the Navy
- Seana Kofoed, actress, Men in Trees
- Mort Kondracke, political commentator, columnist for Roll Call
- George Kontos, relief pitcher for the San Francisco Giants
- Olof Krans, Swedish-American Folk Art painter and artist.
- Ray Kroc, entrepreneur/owner of McDonald's fast food restaurants
- Alison Krauss, bluegrass musician and composer
- Candace Kroslak, actress, Ocean Ave.
- Ken Kwapis, film and television director, The Office, The Bernie Mac Show, Malcolm in the Middle
Read more about this topic: List Of People From Illinois