The exact length of Tran Van Hay's unwashed hair was unclear but some estimates put it as long as 6.8 metres.
China's Xie Qiuping is on record as having the world's longest hair, measured at 5.6 metres in 2004, according to the Guinness World Records.
Hay began to let his hair grow more than 50 years ago because he often got sick after a haircut, the Vietnam News quoted his wife, Nguyen Thi Hoa, as saying.
Media reports said he lived a simple life as a herbalist, but his hair could complicate things. Reports said no motorcycle taxi would carry him because he could not wear a helmet. In the daytime he balanced his hair on his head like a basket, protected by a scarf.
Hay, whose hair weighed several pounds, died at home Wednesday in the southern province of Kien Giang at the age of 79, Vietnam News said.