2018 US Open – Boys' singles

Wu Yibing was the defending champion, but was no longer eligible to participate in junior tournaments.

Thiago Seyboth Wild won the title, defeating Lorenzo Musetti in the final, 6–1, 2–6, 6–2.

Seeds
• # Tseng Chun-hsin (semifinals)

• # 🇦🇷 Sebastián Báez (second round)

• # 🇫🇷 Hugo Gaston (third round)

• # 🇨🇴 Nicolás Mejía (third round)

• # 🇰🇿 Timofei Skatov (second round)

• # 🇧🇷 Thiago Seyboth Wild (champion)

• # 🇧🇬 Adrian Andreev (first round, retired)

• # 🇯🇵 Naoki Tajima (first round)

• # 🇧🇷 Gilbert Soares Klier Júnior (first round)

• # 🇦🇷 Facundo Díaz Acosta (first round)

• # 🇺🇸 Tristan Boyer (first round)

• # 🇨🇳 Mu Tao (first round)

• # 🇷🇴 Filip Cristian Jianu (first round)

• # 🇺🇸 Brandon Nakashima (quarterfinals)

• # 🇪🇸 Carlos López Montagud (first round)

• # 🇹🇷 Yankı Erel (first round)

Seeds
• # 🇫🇷 Valentin Royer (qualified)

• # 🇧🇷 Mateus Alves (qualified)

• # 🇵🇱 Wojciech Marek (qualified)

• # 🇦🇷 Alejo Lorenzo Lingua Lavallén (qualifying competition)

• # 🇮🇹 Giulio Zeppieri (qualified)

• # Admir Kalender (first round)

• # 🇺🇿 Sergey Fomin (first round)

• # 🇬🇧 Jacob Fearnley (qualifying competition)

• # Henry von der Schulenburg (qualified)

• # 🇮🇹 Matteo Arnaldi (first round)

• # 🇷🇴 Cezar Crețu (qualified)

• # 🇩🇪 Justin Schlageter (first round)

• # 🇮🇹 Davide Tortora (first round)

• # 🇩🇪 Henri Squire (qualifying competition, lucky loser)

• # 🇺🇸 Eliot Spizzirri (qualified)

• # 🇮🇳 Siddhant Banthia (first round)

Qualifiers
• # 🇫🇷 Valentin Royer

• # 🇧🇷 Mateus Alves

• # 🇵🇱 Wojciech Marek

• # Henry von der Schulenburg

• # 🇮🇹 Giulio Zeppieri

• # 🇺🇸 Eliot Spizzirri

• # 🇺🇸 Axel Nefve

• # 🇷🇴 Cezar Crețu

Lucky loser

 * 1) 🇩🇪 Henry Squire