Japan (日本, Nihon or Nippon^?, officially 日本国 Nippon-koku or Nihon-koku) is an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south. The characters which make up Japan's name mean "sun-origin", which is why Japan is sometimes identified as the "Land of the Rising Sun".

Japan is an archipelago of 6,852 islands. The four largest islands are Honshū, Hokkaidō, Kyūshū and Shikoku, together accounting for 97% of Japan's land area. Most of the islands are mountainous, many volcanic; for example, Japan’s highest peak, Mount Fuji, is a volcano. Japan has the world's tenth-largest population, with about 128 million people. The Greater Tokyo Area, which includes the de facto capital city of Tokyo and several surrounding prefectures, is the largest metropolitan area in the world, with over 30 million residents.

Sumo (相撲, sumō^?) is a competitive contact sport where a wrestler (rikishi) attempts to force another wrestler out of a circular ring (dohyō) or to touch the ground with anything other than the soles of the feet. The sport originated in Japan, the only country where it is practiced professionally. The Japanese consider sumo a gendai budō^{[citation needed]} (a modern Japanese martial art), though the sport has a history spanning many centuries. The sumo tradition is very ancient, and even today the sport includes many ritual elements, such as the use of salt purification, from the days when sumo was used in the Shinto religion. Life as a rikishi is highly regimented, with rules laid down by the Sumo Association. Professional sumo wrestlers are required to live in communal "sumo training stables" known in Japanese as heya where all aspects of their daily lives—from meals to their manner of dress—are dictated by strict tradition.

The demographic features of the population of Japan include population density, ethnicity, education level, health of the populace, economic status, religious affiliations and other aspects of the population.

As of March 2009, Japan's population is 127,076,183, making it the world's tenth most populated country. Its size can be attributed to fast growth rates experienced during the late 19th and early 20th centuries.

After having experienced net population loss over a number of years, due to falling birth rates and almost no net immigration, despite having one of the highest life expectancies in the world, at 81.25 years of age as of 2006,, Japan's population rose for a second year in a row in 2009, mainly due to the fact that more Japanese returned to Japan than left.

The population of Japan in 2000, in the exact beginning of the year 2000, was 127 million. Its population density was 336 people per square kilometre.

The population ranking of Japan dropped from 7th to 8th in 1990 and from 8th to 9th in 1998 and 10th afterwards.