See main article: 2003 AIG Japan Open Tennis Championships.
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.
The first two seeds received a bye into the second round.