Gabriele Grunewald, the US distance runner hailed as an inspiration for her spirit in fighting cancer for 10 years, has died at the age of 32.
Grunewald - the US champion over 3,000m indoors in 2014 - is the 12th-fastest American woman in history over 1500m.
World marathon record holder Paula Radcliffe praised her determination, while others left messages on the #bravelikegabe hashtag.
Her husband wrote on Instagram that she died "peacefully with no suffering".
"At 7:52 I said 'I can't wait until I get to see you again' to my hero, my best friend, my inspiration, my wife," wrote Justin Grunewald.
"I always felt like the Robin to your Batman and I know I will never be able to fill this gaping hole in my heart or fill the shoes you have left behind. Your family loves you dearly as do your friends.
"To everyone else from all ends of the earth, Gabriele heard your messages and was so deeply moved. She wants you to stay brave and keep all the hope in the world. Thanks for helping keep her brave in her time of need."
The US Olympic Committee paid tribute, posting on Twitter: "Thank you for teaching us what it means to be brave and courageous. Your story and memory will inspire the Team USA family for a lifetime."
World, European and Commonwealth medallist Jo Pavey tweeted: "The running community has lost someone very special. A truly inspiring and courageous person. Thinking of Gabe's family and friends."
Grunewald continued to train and race despite her cancer diagnosis that saw her have several treatments to rid her of the illness, including having half of her liver removed in 2016.
After having radiotherapy during her second cancer treatment in 2011, she finished fourth in the US 1500m trials for the 2012 London Olympics, missing out on a place in the team by one position.
Grunewald, who often trained with her husband on the banks of the Mississippi River in Minneapolis, thought she was cancer free in 2016 - but within two years, scans showed she needed further treatment.
On Monday, Justin used social media to state Grunewald had been admitted to end-of-life care.
In addition to Radcliffe, 2006 London Marathon winner Deena Kastor, and American distance runner Kara Goucher thanked Grunewald for her inspirational attitude prior to her death.