Who invented the shotgun?

Answer 1

This is somewhat akin to asking "Who first came up with throwing rocks?".

The earliest firearms were large bore, unrifled, bronze or iron tubes which were loaded with a charge of black powder followed by lead balls, handfuls of stones, scraps of iron, whatever was at hand that fit down the bore and might inflict damage if thrown hard enough.

Since a shotgun can be loosely defined as a smooth-bore (unrifled) weapon capable of firing multiple projectiles (a load of shot, for example), the very first firearms were essentially shotguns. Who made the first one has been debated for a long time and probably will never be answered. Roger Bacon is sometimes credited with the invention of gunpowder in 1249 but he is only the first European to have written down a crude recipe, likely copied from earlier Arab sources and the Chinese had been using black powder much earlier though only in fireworks. The siege of Metz in 1324 is believed to be the first use of black powder cannons in warfare. So, who "invented" the shotgun? No one knows.