The crash occurred at about 9:03 p.m., in the 4800-block of West Diversey Avenue.
Police said a woman driving an SUV was turning into a parking lot when she hit an ATV driven by a 22-year-old man who had a 16-year-old boy riding with him.
The driver of the ATV was transported to Lutheran General Hospital, where he was listed in critical condition, police said.
The passenger was transported to Lutheran General Hospital, where he was listed in good condition, police said.
No other injuries were reported and citations are pending, police said.
INTERACTIVE SAFETY TRACKER Track crime and safety in your neighborhood