Though ancient inscriptions provide us with the names of almost 400 Celtic deities, a fair amount of these are seen only once, accompanied by no description. We must therefore assume that these specific gods and goddesses were tribal or familial. Other god names are elaborated on with descriptions, or sometimes paired with one of the Roman gods. The functions of the Roman gods are better known, so we can discern the purpose of their Celtic counterparts. Some names are thought to be only one of many used to represent the same deity. This would be like the fact that the Greek Zeus, the Roman Ispater, and many Hindu and Germanic gods have multiple names. In one Roman inscription, over 50 Celtic god names were associated with the Roman god Mars. It is then possible that these 50 were all used to represent an identical god. The true names of the gods were probably too sacred to be heard or written and kept as a secret, or they were blended into the different local names.
Contrary to some other religions such as Christianity, the Celts seemed to think of the Earth and the Otherworld as one unified place. The gods were said to live among them. This can be seen in the fact that a number of mountains, rivers, and natural locations were named after gods. These gods were inseperable from their environment. For the Celts, all gods were descended from one, which is what distinguished them from the mortals. For example, the whole of the Irish pantheon was descended from Danu, the mother goddess. This group of gods is thus called the Tuatha de Danann, or the "Tribe of Danu".
There are two main theories about the structure of Celtic mythology. One states that there were three main types of gods: warriors, craftsmen, and agricultural gods. The more recent theory, which is backed up by some historical evidence, places each god into one of three realms. This system could be compared to that of Norse mythology, which assigns gods to one of either Asgard, Midgard, or Niflheim, their version of the three realms. The realms are said to the the Upper, Lower, and Middle realms. These realms might also represent the Sky, Water, and Earth. The variety of sacrifices offered by the Celts lend support to this theory. Bodies were cremated to be sent to the gods of the Sky realm. Some were buried for the Earth gods. Still others were deposited in water.
On this page, the mythology has been split into five different sections for easier navigation. The Irish, Welsh, British, Gallic, and General Celtic sections each offer information on the main gods, heroes, and personalities of each region.