The French commune of Rouchefourchat has exactly one inhabitant.
I imagine that would make mayoral elections rather boring.
Joking aside, do such tiny municipalities even have a mayor or local government with any practical power or responsibilities? Or does, for all practical purposes, the communauté de communes take over this role? In case of Rochefourchat, the Communauté de communes du Diois unites 50 communes and has a total of 11688 inhabitants, which seems more practical for purposes of local administration and politics.
According to this undated list, there are (or were) 93 communes in France with less than twenty residents including 19 with less than ten residents, so although Rochefourchat is an extreme example¹, it is not alone in being tiny.
¹Discounting nine villages destroyed in World War I and retained for historical purposes.