2004 AIG Japan Open Tennis Championships – Women's singles

Maria Sharapova was the defending champion and successfully defender her title, by defeating Mashona Washington 6–0, 6–1 in the final.

Seeds
The first two seeds received a bye into the second round. • # 🇷🇺 Maria Sharapova (champion)

• # 🇫🇷 Tatiana Golovin (second round)

• # 🇯🇵 Shinobu Asagoe (first round)

• # Kristina Brandi (second round)

• # 🇺🇸 Meghann Shaughnessy (first round)

• # 🇦🇺 Nicole Pratt (first round)

• # 🇨🇿 Klára Koukalová (semifinals)

• # 🇪🇸 Arantxa Parra Santonja (first round)