With a population around at 124.7 million in July 1993, Japan is three times more densely populated than Europe as a whole and twelve times more densely populated than the United States. The population has more than tripled since 1872, when it stood at 34.8 million. Beginning in the 1950s, the birth rate declined, and by 1993 the rate of natural increase was 0.32 %, the lowest in the world outside Europe. Both the density and the age structure of Japan's population are likely to determine the nation's future.

Japan ranks as the world’s ninth most populous nation, with a population of 126,772,660 (2001 estimate). It is also one of the most crowded, with an average population density of 336 persons per sq km .The population is distributed unevenly within the nation. The most crowded area is central Tokyo, where overall population density is about 13,000 persons per sq km.

The Japanese people are members of the Asiatic geographic race and are closely akin to the other peoples of eastern Asia; they constitute the overwhelming majority of the population. During the Tokugawa time, there was a social division of the populace into four classes , with a peer class above and an outcast class below. With the exception of the burakumin, the descendants of the former outcast class, this social-class system has almost disappeared. The burakumin, are still subject to varying degrees of discrimination.