She continuing to compete at a world class level long after being diagnosed.
Her death was announced on Instagram by her husband Justin.
"I always felt like the Robin to your Batman and know I will never be able to feel this gaping hole in my heart or fill the shoes you have left behind," Justin wrote.
"To everyone else from all ends of the earth, Gabriele heard your messages and was so deeply moved."
Three years after her initial cancer diagnosis, Grunewald finished fourth at the U.S. Olympic trials in 2012, narrowly missing a spot on the team for the London Games.
She did, however, represent the U.S. at the 2014 world indoor championships.
She also competed at the 2016 U.S. Olympic trials.
World marathon record-holder Paula Radcliffe was among those saddened by Grunewald's plight.
"The bravery, heart and smile of @gg_runs will always shine brightly and inspire so many," Radcliffe tweeted on Sunday when news broke that Grunewald's death was imminent.
(Reporting by Andrew Both in Cary, North Carolina)
