Hunger by Knut Hamsun, 1890. I consider it the first psychological novel.<p>"The novel has been hailed as the literary opening of the 20th century[1] and an outstanding example of modern, psychology-driven literature.[2] Hunger portrays the irrationality of the human mind in an intriguing and sometimes humorous manner."
<a href="https://en.wikipedia.org/wiki/Hunger_(Hamsun_novel)" rel="nofollow">https://en.wikipedia.org/wiki/Hunger_(Hamsun_novel)</a>