"Game of Thrones" star and strongman legend Thor Björnsson just shared devastating news ... his daughter passed away this week after his wife suffered a delayed miscarriage.
Björnsson and fitness model Kelsey Henson announced they were expecting their second child together last month -- due in March 2024 -- but tragically, she suffered a stillbirth.
"It is with great sorrow that we announce the birth of our daughter, Grace Morgan Hafthorsdottir born Nov 8th at 21 1/2 weeks gestation," the 34-year-old said on Instagram.
"After a noticeable decrease in movement we found out her heart had stopped beating."
Thor shared photos of him and Henson -- who married in 2018 -- with their daughter in the hospital bed ... as well as their son Stormur holding his baby sister (WARNING: IMAGES ARE GUTWRENCHING).
"Words cannot describe our pain of this loss or our happiness at being able to spend time with our daughter," Bjornsson said.
"The grief we feel will be with us forever but so will the love. All of our hopes and dreams for her have been taken away from us but I know I will be with her again."
Thor added, "Her spirit lives on through us and her siblings. We ask that you respect our privacy at this time as we grieve this unbearable loss. Thank you all for any kind words and support."
Fans and star athletes alike left supporting messages under the post, including 7x Mr. Olympia Phil Heath who said, "We’re lifting you both up in prayer and love."