2004 US Open – Boys' singles

Jo-Wilfried Tsonga was the defending champion, but turned professional during this season.

Gaël Monfils would have been the first junior to achieve a calendar Grand Slam since Stefan Edberg in 1983 but lost in the third round to Viktor Troicki.

Andy Murray won the title by defeating Sergiy Stakhovsky 6–4, 6–2 in the final. It was the 1st and only Grand Slam title in his Juniors career. Murray would go on to win the senior title in his maiden Grand Slam title eight years later.

Seeds
• # 🇫🇷 Gaël Monfils (third round)

• # 🇩🇪 Andreas Beck (semifinals)

• # 🇬🇧 Andy Murray (champion)

• # 🇺🇸 Alex Kuznetsov (second round)

• # 🇺🇸 Brendan Evans (second round)

• # 🇦🇷 Eduardo Schwank (third round)

• # 🇺🇦 Sergiy Stakhovsky (final)

• # 🇩🇪 Mischa Zverev (semifinals)

• # 🇩🇪 Sebastian Rieschick (first round)

• # 🇺🇸 Scoville Jenkins (quarterfinals)

• # 🇺🇸 Scott Oudsema (third round)

• # 🇪🇸 Pablo Andújar (first round)

• # 🇮🇳 Karan Rastogi (first round)

• # Igor Sijsling (first round)

• # 🇮🇹 Fabio Fognini (second round)

• # Viktor Troicki (quarterfinals)