Mountain Day (Japan)

Mountain Day refers to three different and unrelated events: (1) Mountain Day, a student celebration in some colleges in the United States in which classes are cancelled without prior notice, and the student body heads to the mountains or a park, (2) International Mountain Day, held each year on 11 December, which was established by the UN General Assembly in 2003 to encourage sustainable development in mountains, and (3) Mountain Day, a national holiday in Japan as of 2016.

Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asian mainland, it is bordered to the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea in the south. The Japanese archipelago consists of four major islands alongside 14,121 smaller islands, covering 377,975 square kilometers (145,937 sq mi). Divided into 47 administrative prefectures and eight traditional regions, about 75% of the country's terrain is mountainous and heavily forested, concentrating its agriculture and highly urbanized population along its eastern coastal plains. With a population of over 123 million as of 2025, it is the 11th most populous country. The country's capital and largest city is Tokyo.