Ontario Provincial Police are investigating the crash that happened at about 10 p.m. ET Saturday near Frankford, Ont., just less than a three-hour drive southwest of Ottawa and north of Belleville.
Police say an all-terrain vehicle carrying two men struck a tree, killing the 21-year-old driver from Marmora, Ont.
Another 21-year-old from Trenton, Ont., who was the passenger, was sent to Trenton Memorial Hospital in critical condition. He was then transferred to Kingston General Hospital.
The names of the victims have not been released.
OPP continue to investigate.