Kokoro (こゝろ, or in post-war orthography こころ) is a novel by the Japanese author Natsume Sōseki. It was first published in 1914 in serial form in the Japanese newspaper Asahi Shinbun. While the title literally means "heart", the word contains shades of meaning, and can be translated as "the heart of things" or "feeling". The work deals with the transition from the Japanese Meiji society to the modern era, by exploring the friendship between a young man and an older man he calls "Sensei" (or teacher). It continues the theme of isolation developed in Soseki's immediately preceding works, here in the context of interwoven strands of egoism and guilt, as opposed to shame. Other important themes in the novel include the changing times (particularly the modernization of Japan in the Meiji era), the changing roles and ideals of women, and intergenerational change in values, the role of family, the importance of the self versus the group, the cost of weakness, and identity.
During the novel's initial serial run, from April 20 to August 11, 1914, it was printed under the title Kokoro: Sensei no Isho (心 先生の遺書, Kokoro: Sensei's Testament). When later published in novel form by Iwanami Shoten, its title was shortened to Kokoro; the rendering of the word "kokoro" itself was also changed from kanji (心) to hiragana (こゝろ).