Mr Weider, the founder of the International Napoleonic Society, received confirmation from an American laboratory of arsenic concentrations in the emperor's hair five years ago.
According to two French forensic specialists in Strasbourg, tests on five strands of Napoleon's hair preserved since his death confirm "major exposure to arsenic".
Napoleon, who was born in Corsica, died at the age of 52 on 5 May 1821, on the island of St Helena in the south Atlantic Ocean, where he had been banished after his defeat at Waterloo.
Officially, he was said to have died of stomach cancer.
Poison theory
According to Pascal Kintz, one of the two Strasbourg Forensic Institute's experts, "the level of arsenic found in Napoleon's hair is higher than 7 to 38 times normal amounts and is an unmistakable sign of poisoning".
The analysis was commissioned by Ben Weider, a Canadian millionaire businessman and Napoleon enthusiast who for years has defended the poison theory.
Mr Weider, the founder of the International Napoleonic Society, received confirmation from an American laboratory of arsenic concentrations in the emperor's hair five years ago.
A year ago, he presented French journalists with evidence of his claims.
One theory for the presence of the arsenic is that it was found in paint or wallpaper in Napoleon's room on St Helena, or that the local water was contaminated with it.
But the experts ruled this out, saying the amounts showed it must have been deliberately administered.
English conspiracy
Against the opinion of mainstream historians, Mr Weider argues the British governor of St Helena, Hudson Lowe, conspired with French count Charles de Montholon to assassinate Napoleon for fear he would escape from the south Atlantic island and return to France.
But according to others, it was in fact one of Napoleon's aides on the island who gave him the poison, with the intention of making him ill and thus persuading the English to let him back to France.
Napoleon, who rose swiftly through the ranks of the revolutionary French army, proclaimed himself emperor in 1804.
He was exiled a first time to the Mediterranean island of Elba in 1815 before returning for a Hundred Day rule, which ended with defeat by the English at Waterloo, and a second exile.
Mr Weider plans to ask the French Government to open Napoleon's tomb at the Hotel des Invalides in Paris to compare the DNA in the hair samples with that of his remains.