Allyson Felix runs in the women's 400 meters heats during the Tokyo Olympic Games on August 3, 2021 in Tokyo, Japan. Photo: VCG

US track and field great Allyson Felix confirmed Wednesday she will retire this year, bringing the curtain down on a career that spanned three decades and included a record-setting 11 Olympic medals.

The 36-year-old said in an Instagram post she planned to embark on her farewell season as a gesture of gratitude to the sport.

"I have given everything I have to running and for the first time I'm not sure if I have anything left to give," Felix said.

"I want to say goodbye and thank you to the sport and people who have helped shape me the only way I know how - with one last run," she added.

"This season isn't about the time on the clock, it's simply about joy."

Felix did not give details of her competitive schedule, but it is likely she is targeting this year's World Championships, which will be held in Eugene, Oregon in July.

Felix is the most decorated woman in the history of Olympic track and field, winning the first of her 11 medals at the 2004 Olympics in Athens and the last at last year's Tokyo Games, a gold in the 4x400 meters relay.

She is also the most decorated athlete - male or female - in the history of the World Championships with 18 medals, seven from individual events and 11 from relays.

Gold medal winner Allyson Felix stands on the podium after the women's 4x400 meters relay at the Tokyo Olympic Games on August 7, 2021 in Tokyo, Japan. Photo: VCG

Felix took part in last year's pandemic-delayed Tokyo Olympics three years after giving birth to daughter Camryn in 2018 after an emergency C-section.

She has since been a vocal advocate for the rights of working mothers and split with longtime sponsors Nike in 2019 after criticizing the sporting apparel giant for slashing her pay after she became pregnant.

"If we have children, we risk pay cuts from our sponsors during pregnancy and afterward," Felix wrote in a New York Times editorial at the time. 

"It's one example of a sports industry where the rules are still mostly made for and by men."

Felix's criticism prompted Nike to swiftly change its policy, vowing to ­ensure no female athlete would in future be impacted financially by pregnancy.

Felix said Wednesday that her advocacy for women would be a theme of her farewell season.

"This season I'm running for ­women," she wrote. "I'm running for a better future for my daughter. I'm running for you. 

"More to come on that, so stay tuned, but I'll be sharing a series of announcements that I'm hoping will make the world better for women. Here's to my final season."