If we consider "a society" to be a group of individuals within the same species who cooperate for the benefit of the group as a whole, then it is reasonable to say that all human societies are hierarchical to some degree.
Several well known philosophies aspire to a society entirely without hierarchy. However looking at nature for inspiration doesn't help much as it seems that all social animals from mammals, to birds, to fish to insects have a hierarchical social structure. From an evolutionary perspective it can be argued that this makes sense as without a social structure aggression and violence is much more likely in order to assert access to food and breeding rights, sacrificing rank in society for a low risk albeit slightly reduced access to food and mates could therefore be a sensible trade off. In addition leadership prevents group fragmentation and subsequent vulnerability to predators.
The question is therefore is hierarchy inherent to and/or necessary for the existence of Society?