The race was only Sir Mo's third marathon and he won with a European record time of 2 hours 05min 11sec. 

Ethiopia's Mosinet Geremew Bayih came in second with 2:05:24 and Japan's Suguru Osako finished third with 2:05:50.

The European record had previously been held by Norway's Sondre Nordstad Moen, who set the time of 2:05:48 in 2017 at the Fukuoka Marathon in Japan.

Sir Mo retired from track athletics in August 2017 to concentrate on road racing following a successful career in the 10,000 and 5,000 metres, winning four Olympic gold medals at London 2012 and Rio 2016. 

He finished third in this year's London Marathon. 

The Chicago Marathon, the fifth race in this year's six-event Abbott World Marathon Majors, was hampered by heavy rain and cold conditions.

"The conditions weren't great and everyone was thinking about conditions rather than time, but towards the end we picked it up," Sir Mo said. 

"I felt good towards the end of the race. 

"At the beginning I felt a bit sluggish but overall I'm very happy with it."

Brigid Kosgei of Kenya won the women's race in 2:18:35. 

She had finished as runner-up in the 2018 London Marathon and in last year's Chicago Marathon. 

Rosa Dereje of Ethiopa finished second with 2:21:18 and compatriot Shure Demise came in third with 2:22:15. 

In the women's wheelchair race, Manuela Schar of Switzerland eased to victory with a time of 1:41:38.

Madison De Rozario of Australia placed second with 1:43:16 and in third was Susannah Scaroni of the United States with a time of 1:44:48.

American Daniel Romanchuk just beat Marcel Hug of Switzerland by one second to win the men's wheelchair race with a time of 1:31:34.

Britain's David Weir came in third with a time of 1:31:43.