Douglas died Sunday at his sister's home in the desert resort town of La Quinta surrounded by family and friends, said commission spokeswoman Sarah Christie.
Douglas, who had been battling lung cancer, retired in November from the agency he founded.
"He was a remarkable person and a wonderful spirit," Christie said. "His name is synonymous with the coast."
In the 1970s, Douglas co-authored a ballot initiative that created the coastal commission, and he later helped draft legislation that would become the nation's most stringent coastal protections.
Douglas' tenure was not without controversy. He often sparred with developers and property owners, and he weathered nearly a dozen attempts to unseat him over the years.
Douglas is survived by his former wife, two sons and a sister and brother.