Danu, Anu, or Dana, is the ancient Mother goddess of the Tuatha Dé Danann pantheon. Danu was worshipped by the Sidhe race, the Celtic tribes that first invaded Ireland. She is particularly associated with the province of Munster with its fertile soil and was known as Anu in those parts. The Tuatha Dé Danann were all descended from her.
She is a water goddess too, thought to share her name with the river Danube because her name implies fresh, running water. It is also thought that she may be a goddess of war.
Some believe that Anu was the primary Earth Goddess and Danu was only the name given to her by the nineteenth century writers.