The Japanese name for Japan, 日本, can be pronounced either Nihon or Nippon. Both readings come from the onyomi.

日 ("nichi") means "sun" or "day"; 本 ("hon") means "base" or "root". The compound means "base of the sun" or "sunrise"; it is of course a source for the popular Western description of Japan as the "Land of the Rising Sun".

"Nichi", in compounds, usually loses the final "chi" and creates a slight pause between the first and second syllables of the compound. When romanised, this pause is represented by a doubling of the first consonant of the second syllable; thus Nichi 日　plus Kou 光 (light) is written and pronounced Nikkou, meaning sunlight. Hon in compounds also often changes to "bon" or "pon"; H, B and P are closely related sounds in Japanese.

There are therefore two possible pronunciations for 日本: Nihon or Nippon.

While both pronunciations are correct, Nippon is frequently preferred for official purposes, including money, stamps, and international sporting events, as well as the Nipponkoku, literally 'The Nation of Japan' (日本国).

Other than this, there seem to be no fixed rules for choosing one pronunciation over the other; in some cases one form is simply more common. For example, Japanese people most often call themselves Nihonjin and their language Nihongo; "Nipponjin" and "Nippongo" are unusual but not incorrect, and can be found in certain regional dialects. In other cases, uses are variable. The name for the Bank of Japan (日本銀行), for example, is given as NIPPON GINKO on banknotes, but often referred to (in the media, for example) as Nihon Ginkō.

Nippon is used most often in the following constructions:

• Nippon-koku kenpo (Constitution of Japan)
• Gambare Nippon! (A sporting cheer used at international sporting events, roughly, 'hang in there Japan!')
• Nippon-bashi (日本橋) (a town in Osaka where electronic goods stores are gathered)

Nihon is used most often in the following constructions:

• Nihon-jin (Japanese people)
• Nihon-go (Japanese language)
• Nihon-shoki (an old history book, never Nippon-shoki)
• Nihon-bashi (日本橋) (oldest and largest commercial districts in Tokyo)
• Nihon-kai (Sea of Japan)