Savannah Chrisley's ex-fiancé, Nic Kerdiles, had alcohol in his system when he died earlier this year after a fatal motorcycle crash ... this according to the medical examiner.

According to the autopsy report, obtained by TMZ, the ME in Nashville found evidence of ethanol in Kerdiles' bloodstream after toxicology tests were done ... and they estimate his BAC at about 0.124, well over the legal limit.

Officials note Kerdiles' body was pretty banged up as a result of the accident -- including multiple broken bones, bruising of the brain and other abrasions. The Medical Examiner found the cause of death to be multiple blunt traumatic injuries ... ruling it as accidental.

TMZ broke the story ... Kerdiles -- a former NHL player for the Anaheim Ducks -- collided with a car while riding late at night one weekend back in September, when cops say he blew past a stop sign and struck the side of a crossing BMW.

It was an absolute tragedy, especially considering his last official photo on social media -- which literally showed him riding his bike, and labeling himself a "Night rider."

Savannah, who'd been engaged to Nic between 2018 and 2020, was devastated by the news ... and posted a tribute to Nic in the aftermath, writing -- "Heaven gained the most beautiful angel today ... I miss you and I love you," while adding, "We loved hard ... and I can't wait to ride bikes with you along the beaches of heaven one day."

Before they ended their relationship, Nic had been featured on her family's show, "Chrisley Knows Best" ... and his proposal to her was even captured on camera.