A thousand years have passed since the fall of industrial civilisation during the "seven days of fire", a planetary war of immeasurable violence. Humanity survives as best it can in a few enclaves threatened by the fukai, a gigantic forest that is constantly gaining ground and whose spores are deadly to most living beings. This thick jungle is protected by giant insects that have adapted to this environment. The "ômus" are the main representatives of these insects, due to their size and sensitivity.

The Valley of the Wind is a small agricultural kingdom, protected from spores and fukai by sea winds. Its tranquillity is disrupted by the sinking of a huge ship of the Tolmec Empire, which has been targeted by insects since an unfortunate stop in the poisonous forest. In order to retrieve the ship's cargo, Tolmec troops invade the valley; they murder the old king Jill and take his daughter Nausicaä prisoner.

It turns out that this cargo, so precious to the Tolmecs, is a giant warrior descended from the colossi who destroyed the world during the "seven days of fire". The Tolmecs want to use it to burn down the poisonous forest, to the detriment of the neighbouring peoples they are at war with. This fire could provoke the wrath of thousands of ômus and their tidal wave would be devastating as it had been in the past when they had caused the annihilation of entire nations.

Nausicaä, managing to escape, discovers that the fukai does not poison the environment, but that it purifies it by draining the polluted air and soil. Guided by her love for all living beings and accompanied by her pet Teto, she will try by all means to silence the war, save humanity and restore a balance between Man and nature.