In Irish mythology, the goddess associated with the river Shannon is Sionna. She represents the river's spirit and essence and is integral to the landscape's mythology. The story suggests that she was transformed into the river after a mystical encounter with a hazelnut tree. The river Shannon, named after her, symbolizes fertilization, life, and the fusion of the natural and spiritual worlds. Sionna's narrative emphasizes the deep connection between landscape features and divine beings in Irish lore, illustrating how myths shape cultural identity and regional significance.