Izzi Batt-Doyle smashes Australian marathon record with run in Chicago

Adelaide's Izzi Batt-Doyle is Australia's new marathon queen after breaking the national record with a stunning run at the year's penultimate major, the Chicago Marathon.

Batt-Doyle ran a time of 2:20:38 to take 46 seconds off the mark set by fellow South Australian Jess Stenson in Valencia last December.

It also lowered the 31-year-old's own personal best by two minutes and 21 seconds.

"I'm very, very happy. I feel a sense of relief, because it's something I really felt I could achieve and it's been on my mind the past couple of years," Batt-Doyle said.

"I'm really proud I could achieve it today and I'm so happy."

Batt-Doyle was sixth overall in the women's race, which was won by defending champion Hawi Feysa of Ethiopia in 2:13:33.

"The field here is so great, but smaller on the professional side," said Batt-Doyle.

"You don't have masses of people in groups."

Batt-Doyle was paced by her fiancé Riley Cocks.

"(We were) isolated the whole race," she said.

"The gun went off and second kilometre it was just the two of us, because we were running between groups.

"I spent most of the race trusting our plan and the pacing strategy we had hoped to run the first half in, and hope that I would feel strong in the second half."

Batt-Doyle's race was a model of control, with her splits barely moving. Every 5km block landed between 16:36 and 16:47, holding her at about 3:19 to 3:21 per kilometre from the opening kilometres to the final stretch.

She went through halfway in 1:10:29 and then ran the second half in about 1:10:09, giving her a 20-second negative split.

"We went through halfway in under the time needed to run 2:21, but I wasn't sure because I felt like I was slowing in the second half as it was warmer, and just the general fatigue of the marathon," Batt-Doyle said.

"It was quite warm and we knew going into this week that it was going to be a bit warmer than ideal marathon conditions, but we did what we could do to prepare for that.

"That's hydrating a lot beforehand, and every opportunity that there were water cups I was splashing three or four water cups to keep cool."

But Batt-Doyle didn't fade in the conditions, with her quickest 5km split of 16:36 coming between 35km and 40km. She covered the last 2.2km at about 3:14 per kilometre, when she started to sense the record was hers.

"There is a small hill about 400 to go, and then you turn into the last 150 metres, and I saw the clock and that's when I really started celebrating," she said.

"It was quite emotional. You can think you can do it and hope you can do it, and be on pace to do it, but there is so much that can happen in the last five kilometres, or last one kilometre or even the last 400 metres.

"People can cramp and have all sorts of things happen. I feel you can't really celebrate or have that sense of finish line relief until you actually get there."

Batt-Doyle says she's proud to join the list of previous Australian record-holders that includes Stenson, Sinead Diver and Benita Willis.

"I think it's really validating for the hard work I've put in and it feels really special to be part of history, because there have been some fantastic runners before me, and fantastic runners to come," she said.

"I really feel honoured, that sums it up. To be in that class of athletes. I'm really proud of that."