The 2005 AIG Japan Open Tennis Championships was a tennis tournament played on outdoor hard courts. It was the 32nd edition of the event known that year as the AIG Japan Open Tennis Championships, and was part of the International Series Gold of the 2005 ATP Tour, and of the Tier III Series of the 2005 WTA Tour. Both the men's and the women's events took place at the Ariake Coliseum in Tokyo, Japan, from 3 October through 9 October 2005. Wesley Moodie and Nicole Vaidišová won the singles titles.
See main article: 2005 AIG Japan Open Tennis Championships – Men's singles. Wesley Moodie defeated Mario Ančić, 1–6, 7–6(9–7), 6–4 [1]
See main article: 2005 AIG Japan Open Tennis Championships – Women's singles. 
Nicole Vaidišová defeated 
Tatiana Golovin, 7–6(7–4), 3–2, retired[2]
See main article: 2005 AIG Japan Open Tennis Championships – Men's doubles. 
Satoshi Iwabuchi / Takao Suzuki defeated 
Simon Aspelin / 
Todd Perry, 5–4(7–3), 5–4(15–13)
See main article: 2005 AIG Japan Open Tennis Championships – Women's doubles. 
Gisela Dulko / 
Maria Kirilenko defeated Shinobu Asagoe / 
María Vento-Kabchi, 7–5, 4–6, 6–3