It happened at the Central station in the Austin neighborhood. The Cook County Medical Examiner's Office said the victim was 22 years old.
The Chicago Fire Department said a CTA employee was also hospitalized.
Green Line service has been suspended in that area.
The CTA said trains are operating only between Ashland/63rd as well as Cottage Grove and Ashland/Lake. Shuttle buses are available between Harlem/Lake and Ashland/Lake to provide connecting service.