The girl was riding in a car when someone on the street opened fire in the 2300 block of West 72nd Street about 7:50 p.m., Chicago police said.
The girl was wounded in the back of the head and was taken to Comer Children’s Hospital, where she was in critical condition, police said.
Community activist Andrew Holmes told reporters at the hospital that the girl had just turned 12 and is now "fighting for her life."
"We need to seriously start turning these individuals in," Holmes said. "If you have any video surveillance, any knowledge, license plates, anything, it doesn’t matter. This child is fighting for her life."
No one was in custody.
The shooting occurred in the 8th police district, which has seen a 29% increase in shootings this year compared to the same time last year, according to police data. Overall, crime is up 54% in the district, including more aggravated batteries, robberies, burglaries, thefts and motor vehicle thefts.