ATHLETICS: Jess Trengove has become the sixth fastest Australian female marathon runner ever after racing to a commanding victory in the Melbourne marathon.

The 2014 Commonwealth Games bronze medallist sliced almost two-and-a-half minutes off her personal best with a winning time of two hours 27 minutes and 45 seconds on Sunday.

In doing so, Trengove secured an Olympic qualifying time for the Rio 2016 Games. 

"That was what the aim of this year's marathon was - to show that I can do it, that I can line up for Rio and have a real crack," said the 28-year-old Trengove, who first showcased her big-event pedigree with an outstanding 11th-placed finish at the 2013 world championships in Moscow.

"It's not just about being at the Olympics to soak up the experience.

"That's what London was all about - this one is about having a crack.

"I knew I should be able to get this sort of result here if I fuelled myself right and maintained concentration.

"You can have that sort of confidence on the start-line when you know you have done the work, knowing you will run well if you have been smart."

Trengove was accompanied for much of the race by several members of her training group including 2005 world championships 5000m bronze medallist Craig Mottram.

New Zealander Lydia O'Donnell was second in 2:39:01 and Australian Makda Harun Haji was third in 2:40:37.

A spot in the women's marathon next year in Rio is now also right on the agenda for Lisa Weightman.

Racing competitively for the first time since the birth of son Pete in January, the 2010 Commonwealth Games marathon bronze medallist won the Melbourne half-marathon on Sunday in 1:11:00.

"I'm over the moon to run that time and feel so strong," said the 36-year-old Weightman, who will now target the Olympic qualifying mark in January's Houston marathon.

"I had no idea how it would go as I hadn't moved into that phase of training."

The men's marathon was won by Brad Milosevic in 2:16:00, making him the fourth Australian to better the Olympic qualifying mark of 2:17:00 - although only three can compete in Rio.

"It's six months to the day since I DNFed (did not finish a race) in Japan," said the 26-year-old Milosevic.

"It's an IAAF qualifier, so it puts my name in the hat.

"Rio is the dream but then there's also the Gold Coast Commonwealth Games in 2018.

"I've got plenty of years of running left." 

AAP