G
- John Wayne Gacy (1942–1994), serial killer
- Lyman J. Gage, Politician (Republican), Banker and US Secretary of The Treasury
- Johnny Galecki, actor, Roseanne, The Big Bang Theory, American Dreamer
- James Gammon, actor, Nash Bridges, Bagdad Cafe
- Elbert Henry Gary, lawyer, county judge, corporate officer, key founder of U.S. Steel
- Jason Gedrick, actor, Boomtown, Murder One, Sweet Justice
- Willie Geist, host of MSNBC's Way Too Early with Willie Geist and co-host of Morning Joe
- Jami Gertz, actress, Still Standing, Sibs, Twister
- Tavi Gevinson, blogger and feminist
- Marla Gibbs, actress, The Jeffersons, 227, The Hughleys
- Emily Giffin, novelist
- Joe Girardi, manager of the New York Yankees
- Stephen Glass, former journalist for The New Republic fired for serial fraud in his articles
- Caroline Glick, journalist, deputy managing editor for the Jerusalem Post
- Godfrey, comedian, actor
- Jaslene Gonzalez, model and America's Next Top Model, Cycle 8 winner
- Stuart Gordon, director, writer, producer
- Otto Graham, Hall of Fame quarterback for the Cleveland Browns and head coach for the Washington Redskins
- Nancy Lee Grahn, actress, General Hospital, Santa Barbara
- Curtis Granderson, center fielder for the New York Yankees
- Red Grange, college and professional football player
- Ulysses S. Grant, Civil War General and 18th President of the United States 1869–1877
- Bonita Granville, film actress, television producer
- Eli Grba, former MLB relief pitcher, primarily with the New York Yankees
- Andrew Greeley (born 1928), Roman Catholic priest, sociologist and author
- Shawn Green (born 1972), former Major League Baseball 2-time All-Star right fielder
- Kathy Griffin, actress, stand-up comedian, television personality, author, star of My Life on the D-List
- Frank W. Gunsaulus, educator, orator and minister
- Luis Gutiérrez, politician (Democrat), U.S. Representative
- Buddy Guy, blues guitarist and composer
Read more about this topic: List Of People From Illinois