The woman, a homemaker whose name was not released, told police she was walking to church when she was assaulted late Tuesday, police officer Antonio Williams da Silva said by telephone from the northeastern city of Aracaju.
Da Silva said the woman told authorities she hadn't cut her hair for 20 years.
"It must have been nearly a meter and half (more than four feet) long," da Silva said.
The robbers cut the woman's hair above her shoulders, he said, apparently with the idea of selling it to be fashioned into a wig.
"A hairpiece that size could cost you as much" as $550, da Silva said.
The woman was not injured, but her assailants could be charged with battery if caught.
Da Silva said it was the second recent case of hair robbery in Aracaju.
Similar attacks have occurred in other Brazilian cities, where the demand for human hair is high.
