Japanese motion-picture director whose 9 ¹/₂-hour trilogy, Ningen no joken (The Human Condition: No Greater Love, 1959; Road to Eternity, 1959; A Soldier's Prayer, 1961), a monumental criticism of war, constitutes the best example of his films of social concern.

Drafted into the military in 1942, Kobayashi was taken prisoner on Okinawa. In 1946 he was released as a prisoner of war. Returning to Shochiku Motion Picture Company, Tokyo, he served as an apprentice director until he made his debut in 1952 with Musuko no seishun (1952; My Son's Youth). He followed that film with Kabe atsuki heya (1953; The Thick-Walled Room), which criticized the rigid social order that had characterized Japanese life, and Anata kaimasu (1956; I'll Buy You), a film that exposed the commercialism of Japanese baseball.

The Human Condition established Kobayashi's reputation as a major director. It won recognition at international film festivals, as did Seppuku (1962; Harakiri), a film indicting the traditional warrior code of ethics and generally considered his finest film; Kaidan (1964; Kwaidan), a quartet of fantastic ghost stories; and Kaseki (1974; “Fossil”), a dying man's reassessment of life.