Defending champions Jacob Kiplimo of Uganda and Hawi Feysa of Ethiopia will be challenged by a world-class field in the hunt for record times in Sunday's 48th Chicago Marathon.
More than 55 000 runners will compete over the 26.2-mile layout winding through the streets of Chicago, where world records have fallen and could be up for grabs if conditions are favourable.
Kiplimo collected his first marathon triumph last year in Chicago in 2hrs 2mins 23secs in only his second start at the distance.
He added a podium finish in April at a historic London Marathon in which Kenya's Sabastian Sawe won in a world-record 1:59:30 and Ethiopia's Yomif Kejelcha was second in 1:59:41, 47 seconds ahead of Kiplimo.
That marked the first time the mythical two-hour barrier was broken. Kiplimoo's 2:00:28 made him the third-fastest in marathon history and the man to beat in Chicago.
"Coming back to Chicago is my special moment," Kiplimo said. "Winning last year gave me a lot of energy to prepare well."
Kiplimo won the Lisbon Half-Marathon in March in a world-record 57:20 only for Kejelcha to break that mark with a 56:51 triumph in August at Buenos Aires.
Kiplimo, last year's London Marathon runner-up, also won the World Cross Country Championship in January at Tallahassee, Florida.
Kenya's Amos Kipruto, the 2022 London winner who was fourth this year in London at 71 seconds behind Kiplimo, hungers for his first Chicago title after finishing second last year and third in 2024.
"Being in position three in 2024, position two in 2025 and this is 2026 –- I think this is a huge step for me," Kipruto said.
Ethiopia's Milkesa Mengesha, the 2024 Berlin Marathon and 2025 Shanghai Marathon champion, makes his Chicago debut with the third-fastest entry time from his 2:03:17 triumph in Germany.
"People come here to run fast so I'm looking to run my personal best," he said.
On the women's side, Feysa says she is better positioned to win this year than she was in 2025, when she took the title in 2:14:57.
"Compared to last year, I'm in better shape," said Feysa, third at the Tokyo Marathon last March.
The biggest title threat, however, might be Kenya's Brigid Kosgei, who won last year's Shanghai Marathon in a course-record 2:16:36 and took this year's Tokyo title in a course-record 2:14:29 – 3:10 ahead of Feysa.
Kosgei – a two-time winner in London, Tokyo and Chicago – set a then-world record of 2:14:04 in 2019 when she defended her Chicago title.