Nausicaa is the princess of the Valley of the Wind, a small and peaceful kingdom in a post-apocalyptic future where a toxic forest known as the Sea of Corruption or Toxic Jungle has spread across much of the land. She is the eleventh child of King Jihl and the only one to survive to maturity, as her siblings all died from the effects of the poisonous environment. Her mother died when she was very young.

Her personality is defined by a profound compassion that extends to all living things, whether human, animal, or insect. She is courageous, determined, and deeply empathetic, with an ability to sense the feelings of others and communicate with the giant insects that inhabit the toxic forest, especially the Ohm. Despite her gentle nature, she is not passive; she is a capable and skilled warrior who fights when necessary, though she does so reluctantly. Her love for life and her desire for peace are the central forces that drive her actions.

Nausicaa's primary motivation is to understand the world she lives in and to find a way for humanity and nature to coexist. She conducts scientific experiments on samples from the toxic forest in her laboratory, driven by a belief that the ecosystem is not merely a threat to be destroyed but a natural process that may hold the key to the world's recovery. She also feels a strong sense of responsibility to protect her people and later, to intervene in the destructive war between the kingdoms of Torumekia and Pejite.

In the story, Nausicaa acts as a bridge between warring factions and between humanity and nature. After her father is killed during an invasion by Torumekian forces, she assumes leadership of the valley. She becomes caught in a conflict over a dormant giant warrior, an ancient weapon from the war that destroyed the old world. Her actions repeatedly prevent further bloodshed, and she ultimately risks her own life to stop a stampede of enraged Ohm, an act of self-sacrifice that calms the creatures and fulfills an ancient prophecy about a figure in blue who will restore balance to the land.

Her key relationships include her mentor, Lord Yupa, a wandering swordsman and scholar who taught her about the world and respects her growing wisdom. She forms a bond of friendship and mutual trust with Asbel, the prince of Pejite, who initially seeks revenge but comes to share her goals. She also has a complex relationship with Princess Kushana of Torumekia, a pragmatic and ruthless military leader, whose perspective is subtly challenged by Nausicaa's example. Her constant companion is Teto, a small fox-squirrel she tames early in the story.

Throughout the narrative, Nausicaa's character does not undergo a radical change in personality but rather has her innate beliefs tested and validated. Her journey forces her to confront the worst aspects of human fear, hatred, and short-sightedness, yet she remains steadfast in her commitment to empathy and understanding. Her experiences deepen her resolve and prove the strength of her convictions.

Among her notable abilities is her skill as a windrider: she pilots a small, jet-assisted glider called a Mehve with exceptional precision, using her understanding of air currents to fly into dangerous areas. She is also a proficient swordswoman. Her most distinctive ability is her empathic connection with the Ohm and other insects, which allows her to calm them and even sense their emotions and thoughts. This ability is not supernatural in origin but stems from her deep respect and lack of fear toward them. Her scientific curiosity also sets her apart, as she seeks knowledge rather than relying on superstition or dogma.