本论文对小说《白鲸》进行了研究，应用存在主义——二十世纪西方世界最重要的哲学之一——分析亚哈船长这一人物形象。尽管小说主人公亚哈船长的本性早已被激烈讨论过，可他仍旧是一个饱受争议的人物。通过分析存在主义三个主要原则——存在先于本质；世界是荒谬的，人生是痛苦的；自由选择，本论文发现亚哈同时作为无神论者和复仇者而存在，最后得出结论：尽管生活在痛苦之中，亚哈自由选择去追逐白鲸这一行为给予了他存在的意义，也使他成为存在主义意义上的英雄。另外，本论文对未来应用存在主义进行人物分析的其他研究也或有帮助。

This paper puts an investigation into the novel Moby-Dick and applies existentialism, one of the dominant philosophy theories in the western world in the 20th century, to the character analysis of Ahab. The protagonist of the novel, Ahab, whose nature has been intensely discussed, however, remains a controversial character. Through discussing the three main principles of existentialism: existence precedes essence; the world is absurd and life is anguished; free choice, this paper finds that Ahab exists as both an atheist and an avenger, and draws the conclusion that Ahab, while living in anguish, makes free choice to chase the great whale, which gives meaning to his existence and makes him a hero in the sense of existentialism. In addition, this paper hopefully will be helpful to other studies applying existentialism to character analysis in the future.