Leather Armour is, unsurprisingly, armour made from leather and runs the spectrum from lightweight, flexible stuff little heavier than the sort of leather used for clothing to rigid, boiled pieces.
Leather armour requires, perforce, the use of tanned and dressed hides - otherwise it would be hide armour - although the distinction can get mighty blurry around the edges. The heavier pieces are made by boiling thick sections of leather in water or oil to make it shrink and harden - this sacrifices flexibility and is normally used for breastplates, helmets and the like with lighter stuff used for the limbs where flexibility is required. Methods for producing medieval boiled leather (also known as cuir boulli - more or less the same in French) are currently not well understood, but they seem to have created a wide range of rigid but workable pieces which could be substituted for most of the components of plate armour. Despite the hopes of fantasy artists, armourers leather was heavier, coarser stuff than that used in clothing (and until fairly recently, clothier's leather was pretty crude stuff as well) - it could be dyed and finished to some degree but would still have been much uglier than is traditionally depicted and certainly not the patent-leather like stuff often depicted.
Although it was never premier military grade armour, leather had a surprisingly long lifespan, spanning from the pre-metal using era up to the buff coat of early modern times. It was also a popular component in other forms of armour (scale mail for example). It could be reinforced with metal spikes, studs or rings for added protection, but more than a few of these would tend to turn it into ring mail. Arguably leather armour is still in use today in the form of motorcycle leathers and the like and the cowboys in a western campaign will almost certainly derive some protection from their leather chaps, jackets and dusters, even if they won't turn a bullet. Leather also remains useful in applications such as boots, gloves and gauntlets.
Obviously protection is not great - light and cheap are not usually compatible with strong and leather armour is hard to repair - cuts cannot be welded for example, and whilst patching can make for a temporary repair a suit of leather will not last as long as mail.
Game and Story Use
- Leather armour is the traditional protection of Thieves and Rangers in Classic Gygaxian Dungeon Fantasy; and has it's uses outside that genre. How useful it is depends on the realism of the setting and what you want to use the armour for.
- Arguably most people who use armour should be wearing either leather or padded armour in a realistic medieval setting, particularly in peacetime. For most of the period metal armour should be far too expensive and impractical.