Five-hundred to 2,700 people were interviewed by telephone and Internet Oct. 26-Dec. 13 in 51 countries in the BVA-Gallup poll, The Local reported Friday.
France got an overall negative score of 79, the lowest in the history of the poll.
"We have never seen a score this low in 34 years of doing the study," said Celine Bracq of BVA-Gallup.
The second unhappiest country in the survey was Ireland, with a score of negative 68, followed by Austria and Belgium, each with a score of negative 54.
Nigeria was found to be the cheeriest country in the poll, with a positive score of 80, followed by Vietnam at 51, Ghana at 50 and Uzbekistan at 45.
Anthropologist Gilles Boetsch said there were several reasons for gloom in France, including the economy and the uncertain future of social benefits.
"Parents know that their children won't necessarily have a better situation than them," he said.