Japan (Japanese: 日本, Nihon or Nippon), officially the State of Japan (日本国, Nihon-koku), is an East Asian constitutional republic located in the Pacific Ocean, bordered by the Sea of Japan to the west and the Pacific Ocean to the east. Since the end of World War II, Japan has undergone extensive political, social, and cultural transformations, emerging as one of the world’s leading economies and a key regional power in the Asia-Pacific region. 

Its postwar development has been shaped by rapid industrialization, democratic reforms, and close alignment with the United States, while continuing to balance tradition with modernity. However, its contemporary trajectory remains deeply influenced by both the legacy of the U.S. occupation, the Tokyo Insurrection, and unresolved memories of the Imperial era, which continue to shape domestic politics, foreign policy, and historical discourse.

De facto, Japan consists of four main islands (Honshu, Kyushu, Hokkaido, and Shikoku) along with many smaller ones, however, de jure it continues to claim territories administered by the State of Formosa, South Kurile, and other minor islands, reflecting lingering territorial disputes and the enduring shadows of its 20th-century history.