In Norse mythology, the world tree that connects all realms is called Yggdrasil. This enormous tree serves as the axis mundi, linking Asgard, Midgard, and other realms in the Norse cosmos. Yggdrasil represents the interconnectedness of life and death, with various beings inhabiting its branches and roots. It signifies the cycle of existence and the importance of balance in the universe, reflecting the intricate relationships among gods, humans, and the natural world.