A dream vacation turned tragic in Thailand ... an up-and-coming Australian sprint star has died after a motorcycle crash. She was just 25.

Jemma Stapleton was reportedly riding a motorcycle on Thailand's Koh Samui island Wednesday when disaster struck ... with authorities pointing to rainy weather as a possible factor in the crash. Her family was traveling just behind her when it happened.

The tragedy comes just a little over a week after Stapleton celebrated her 25th birthday and months after another standout season on the track. The Melbourne native finished third in the prestigious Stawell Gift in 2025 and returned to the final again this year -- cementing her status as one of Australia's rising sprint talents.

Tributes have poured in from across the athletics world. Stapleton's brother, Joel, remembered her as his "best friend" ... adding that, "For those that knew her, you know how lucky you were to have her in your life."

A fundraiser launched to help the family in the wake of the tragedy quickly drew an outpouring of support -- drawing in more than $100K AUD -- before being closed. Stapleton's loved ones have since thanked supporters and asked for privacy as they grieve the devastating loss.

Jemma spent her life outrunning the competition ... making her sudden death all the more difficult to process.

RIP