Sonoma County Public Health Officer Dr. Mary Maddux-Gonzalez said the teen died of complications from the flu last week after a brief hospitalization.
There have been 36 hospitalizations for the flu in the county and many more reports of influenza-like illnesses, Maddux-Gonzalez said.
"Our deepest sympathies go out to this child's family," Maddux-Gonzalez said in a news release.
"While the vast majority of cases of flu are mild or moderate illnesses, sadly that was not the case here. Every death reminds all of us that influenza can be a very serious illness," Maddux-Gonzalez said.
A vaccine for the H1N1 flu is expected to be available in mid-October.