2009 US Open – Girls' singles

The United States Open Tennis Championships is a hardcourt tennis tournament held annually at Flushing Meadows, starting on the last Monday in August and lasting for two weeks. The tournament consists of five main championship events: men's and women's singles, men's and women's doubles, and mixed doubles, with additional tournaments for seniors, juniors, and wheelchair players.

In 2009, the girls' singles event was won by Heather Watson of the United Kingdom who beat Yana Buchina of Russia, 6–4, 6–1 in the final.

Seeds
• # 🇫🇷 Kristina Mladenovic (first round)

• # 🇹🇭 Noppawan Lertcheewakarn (quarterfinals)

• # 🇭🇺 Tímea Babos (second round)

• # 🇺🇸 Sloane Stephens (third round)

• # Ajla Tomljanović (second round)

• # Silvia Njirić (third round)

• # 🇺🇸 Lauren Embree (second round)

• # 🇺🇸 Christina McHale (withdrew)

• # 🇷🇺 Daria Gavrilova (semifinals)

• # Richèl Hogenkamp (third round)

• # 🇬🇧 Heather Watson (champion)

• # 🇧🇪 Tamaryn Hendler (third round)

• # 🇯🇵 Miyabi Inoue (first round)

• # 🇸🇰 Jana Čepelová (quarterfinals)

• # 🇳🇴 Ulrikke Eikeri (third round)

• # 🇺🇸 Beatrice Capra (quarterfinals)