A
- Jessica Abel, comic book writer and artist
- Flozell Adams, offensive tackle for the Pittsburgh Steelers
- Jane Addams, social worker, teacher, peace activist, Nobel Peace Prize recipient
- George Ade, author
- Paul Adelstein, television actor; Prison Break, Private Practice
- Dankmar Adler, architect
- Scott Adsit, actor, writer, improvisational comedian, 30 Rock, Moral Orel, Mary Shelley's Frankenhole
- Abraham Adrian Albert, mathematician
- Frankie Albert, quarterback and head coach for the San Francisco 49ers and College Football Hall of Famer
- Nelson Algren, author
- Saul Alinsky, founder of modern community organizing and writer
- Joan Allen, actress, The Bourne Ultimatum, The Bourne Supremacy, Face/Off
- Karen Allen, actress, Indiana Jones and the Kingdom of the Crystal Skull, Raiders of the Lost Ark
- Tony Allen, swingman for the Memphis Grizzlies
- Justin Allgaier, sports, 2008 ARCA RE/MAX Series Champion
- Samuel Allison, prominent physicist who worked on the Manhattan Project
- John Peter Altgeld, politician (Democrat), Illinois Governor and workplace safety advocate
- Ken Anderson, former quarterback for the Cincinnati Bengals
- Philip Warren Anderson, Nobel Prize-winning physicist
- Elmer Angsman, running back for the Chicago Cardinals
- Ann-Margret, Emmy-winning actress, singer and dancer
- Philip Danforth Armour, businessman-Founder of Armour and Company
- Matthew John Armstrong, television actor; Heroes, American Dreams
- Louis Armstrong, jazz musician
- Lewis Arquette, actor, Sherlock Hound, Camp Candy, The Waltons
- Patricia Arquette, Emmy-winning actress, Medium
- John Ashcroft, politician (Republican), U.S. Attorney General, Missouri Senator, Missouri Governor
- Jason Avant, wide receiver for the Philadelphia Eagles
- Brendon Ayanbadejo, linebacker for the Baltimore Ravens
- Bill Ayers, founder and former member of the Weather Underground
- Reiko Aylesworth, actress, Michelle Dessler on 24
Read more about this topic: List Of People From Illinois