1999 Japan Open Tennis Championships – Women's singles

The 19999 Japan Open Tennis Championships women's singles was the women's singles event of the twenty-fifth edition of the Japan Open; a WTA Tier III tournament held in Tokyo, Japan. Ai Sugiyama was the defending champion but lost in the final 6–2, 6–2 against Amy Frazier.

Seeds
• # 🇯🇵 Ai Sugiyama (final)

• # 🇺🇸 Amy Frazier (champion)

• # 🇺🇸 Corina Morariu (semifinals)

• # 🇺🇸 Kimberly Po (second round)

• # Kristina Brandi (first round)

• # 🇺🇸 Meghann Shaughnessy (first round)

• # 🇺🇸 Jane Chi (semifinals)

• # Wang Shi-ting (quarterfinals)

Seeds
• # Wynne Prakusya (qualifying competition, lucky loser)

• # 🇰🇷 Kim Eun-ha (second round)

• # 🇰🇷 Cho Yoon-jeong (qualifier)

• # 🇺🇸 Katie Schlukebir (qualifier)

• # 🇯🇵 Misumi Miyauchi (qualifier)

• # 🇯🇵 Akiko Morigami (second round)

• # 🇯🇵 Tomoe Hotta (first round)

• # 🇭🇺 Adrienn Hegedűs (first round)

Qualifiers
• # 🇯🇵 Misumi Miyauchi

• # 🇰🇷 Cho Yoon-jeong

• # 🇺🇸 Katie Schlukebir

• # 🇬🇧 Hannah Collin

Lucky losers

 * 1)  Wynne Prakusya