2023 Chicago Marathon

The 2023 Chicago Marathon was the 45th edition of the annual marathon race in Chicago, held on Sunday, October 8, 2023. A Platinum Label marathon, it was the fifth of six World Marathon Majors events that were held in 2023. The race also hosted the age group world championships for the year.

Kenyan runner Kelvin Kiptum set a new marathon world record, winning the race with a time of 2:00:35, and beating the previous world record of 2:01:09, set by his compatriot Eliud Kipchoge at the 2022 Berlin Marathon, by 34 seconds. Kiptum broke free from all the other runners by the 35 km (22 mi) mark, and finished the race with a significant negative split. This was Kiptum's third marathon, after he set the course record at the 2022 Valencia Marathon with a time of 2:01:53 in what was the fastest marathon debut ever, and then set another course record at the 2023 London Marathon with a time of 2:01:25.

Dutch runner Sifan Hassan set a new course record by finishing the race with a time of 2:13:44, running the second-fastest marathon by a woman, in what was her second marathon ever. Hassan had debuted at the marathon distance with the 2023 London Marathon, which she won with a time of 2:18:33. Swiss wheelchair athletes Marcel Hug and Catherine Debrunner both set course records with their victories, finishing with times of 1:22:37 and 1:38:44, respectively. The marathon was Debrunner's debut race in the United States; Hug broke his own course record. U.S. runner Jake Caswell claimed victory in the non-binary division with a time of 2:38:05.

A total of 48,398 runners and 45 wheelchair athletes finished the marathon. First-time marathon runner Allison Naval of Evanston, Illinois, was celebrated as the millionth finisher of the Chicago Marathon since the modern incarnation's inaugural race in 1977. Naval completed the marathon with a time of 4:23:13.