2003 AIG Japan Open Tennis Championships – Women's singles

Jill Craybas was the defending champion, but lost in quarterfinals to Arantxa Parra Santonja.

Maria Sharapova won the title by defeating Anikó Kapros 2–6, 6–2, 7–6(7–5) in the final.

Seeds
The first two seeds received a bye into the second round. • # 🇯🇵 Ai Sugiyama (quarterfinals)

• # 🇹🇭 Tamarine Tanasugarn (second round)

• # Katarina Srebotnik (second round)

• # 🇯🇵 Shinobu Asagoe (second round)

• # 🇷🇺 Maria Sharapova (champion)

• # 🇺🇸 Ashley Harkleroad (second round)

• # 🇯🇵 Saori Obata (first round)

• # Emmanuelle Gagliardi (second round)