The Nanboku-chō period (南北朝時代, Nanboku-chō jidai, "South and North courts period", also known as the Northern and Southern Courts period), spanning from 1336 to 1392, was a period that occurred during the formative years of the Muromachi bakufu of Japanese history.

During this period, there existed a Northern Imperial Court, established by Ashikaga Takauji in Kyoto, and a Southern Imperial Court, established by Emperor Go-Daigo in Yoshino.

Ideologically, the two courts fought for fifty years, with the South giving up to the North in 1392. However, in reality the Northern line was under the power of the Ashikaga shogunate and had little real independence.

Since the 19th century the Emperors of the Southern Imperial Court have been considered the legitimate Emperors of Japan. Other contributing factors were the Southern Court's control of the Japanese imperial regalia, and Kitabatake Chikafusa's work Jinnō Shōtōki, which legitimized the South's imperial court despite their defeat.

The consequences of events in this period continue to be influential in modern Japan's conventional view of the Tennō Seika (Emperor system). Under the influence of State Shinto, an Imperial decree dated March 3, 1911, established that the legitimate reigning monarchs of this period were the Southern Court. After World War II, a series of pretenders, starting with Kumazawa Hiromichi, claimed descent from the Southern Court and challenged the legitimacy of the modern imperial line, which is descended from the Northern Court.The destruction of the Kamakura shogunate of 1333 and the failure of the Kenmu Restoration in 1336 opened up a legitimacy crisis for the new shogunate. Furthermore, institutional changes in the estate system (the shōen) that formed the bedrock of the income of nobles and warriors alike decisively altered the status of the various social groups. What emerged from the exigencies of the Nanboku-chō (Southern and Northern Court) War was the Muromachi regime, which broadened the economic base of the warriors, while undercutting the noble proprietors. This trend had started already with the Kamakura bakufu.