“90 Day Fiancé” star Elizabeth Castravet’s father, Chuck Potthast, died from blunt force injuries after falling in a bathtub, TMZ has learned.

TMZ has obtained docs from the Hillsborough County, Florida Medical Examiner … and Chuck’s cause of death in November was listed as blunt impact injuries to the face and neck, including facial lacerations and a fractured C6 vertebra. The report also notes positional asphyxia as a factor.

The medical examiner listed chronic alcohol use, liver cirrhosis, and acute alcohol intoxication as contributing causes … meaning he had consumed a significant amount of alcohol before the fall.

Chuck — who appeared on multiple episodes of “90 Day Fiancé: Happily Ever After?” — had been open about his health struggles … and sure enough, the medical report also documents his history of heavy alcohol abuse.

Elizabeth announced his death on IG in November, just two months after he underwent an extensive 8-hour surgery to repair a hernia and collapsed stomach.

Chuck was 64.