The demographics of Japan include birth and death rates, age distribution, population density, ethnicity, education level, healthcare system of the populace, economic status, religious affiliations, and other aspects regarding the Japanese population. According to the United Nations, the population of Japan was roughly 126.4 million people, which peaked from 128.5 million people in 2010. It is the 6th-most populous country in Asia, and the 11th-most populous country in the world.

Hāfu is a Japanese language term used to refer to a person of half Japanese and half non-Japanese ancestry. A loanword from English, the term literally means "half," a reference to the individual's non-Japanese heritage. The word can also be used to describe anyone with mixed-racial ancestry in general. As many consider Japan to be one of the most homogeneous societies on the planet, children who have one non-Japanese parent are called hāfu Japanese and often face prejudice and discrimination from Japanese citizens of full Japanese descent. Hāfu individuals are well represented in Japanese media and abroad, and recent studies in the 2010s estimate that 1 in 30 children born in Japan are born to interracial couples.