As of March 2009, Japan's population is 127,076,183,[1] 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,[3] mainly because more Japanese returned to Japan than left.

The population of Japan in 2000, at New Year, was 127 million. Its population density was 336 people per square kilometer.

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

Japanese society of Yamato people is linguistically homogeneous with small populations of Koreans (0.6 million), Chinese/Taiwanese (0.5 million), Brazilians (300,000, many of whom are ethnically Japanese), and Filipino (245,518, some being Japanese Filipino; children of Japanese and Filipino parentage).

 Japan has indigenous minority groups such as the Ainu and Ryukyuans and social minority groups like the burakumin.

Japanese citizenship is conferred jus sanguinis, and monolingual Japanese-speaking minorities often reside in Japan for generations under permanent residency status without acquiring citizenship in their country of birth, although legally they are allowed to do so. 

This is because Japanese law does not recognise dual citizenship, and so people becoming naturalised Japanese citizens must relinquish citizenship of other countries. Some ethnic Koreans and Chinese and their descendents (who may speak only Japanese and may never have even visited the country whose nationality they hold) do not wish to abandon this other citizenship.

In addition, people taking Japanese citizenship must take a Japanese name and abandon their foreign name, and some do not wish to do this - although most 'special permanent resident' Koreans and Chinese already use Japanese names, so this is not such an important factor. Nonetheless, some 10,000 Zainichi Koreans naturalize every year.

 Approximately 98.6% of the population is pure Japanese (though technically this figure includes all naturalized people regardless of race) and 99% of the population speak Japanese as their first language. Non-ethnic Japanese in the past, and to an extent in the present, also live in small numbers in the Japanese archipelago.