The Japan Open Tennis Championships, or Rakuten Japan Open Tennis Championships for sponsorship reasons, is a men's professional tennis tournament on the ATP Tour 500 held annually in Tokyo, Japan.

It is played on the outdoor hard courts of the Ariake Coliseum with some exceptions, between 1978 and 1981 it was played on clay courts, while in 2018 the Ariake underwent a renovation in view of the XXXII Games Tokyo Olympics, and that edition took place on the indoor hard courts of the Musashino Forest Sport Plaza.

It opened in 1973 as an event on the men's major circuit, and in 1979 tournaments on the women's major circuit were added. The women's event was held until 2008, in 2009 it was absorbed into the Pan Pacific Open tournament which was held until 2008 at the Tokyo Metropolitan Gymnasium, and in 2009 it was moved to the Ariake Coliseum keeping the Pan Pacific Open name.

The Women's Japan Open, which was part of the WTA circuit, was still held in 2009 and 2010 but was demoted to an ITF Women's Circuit tournament with a $100,000+H prize pool, and was permanently discontinued after the 2010 edition. instead he went on to play the men's Japan Open as part of the ATP Tour 500.

The most successful players are Stefan Edberg and Kimiko Date with 4 wins each. The tournament has been sponsored since 2009 by Rakuten. The 2020 and 2021 editions were not held due to the COVID-19 pandemic.