2021 Knoxville Challenger – Singles

Michael Mmoh was the defending champion but lost in the semifinals to Daniel Altmaier.

Christopher Eubanks won the title after defeating Altmaier 6–3, 6–4 in the final.

Seeds
• # 🇺🇸 Tennys Sandgren (first round)

• # 🇩🇪 Daniel Altmaier (final)

• # 🇨🇦 Vasek Pospisil (first round)

• # 🇺🇸 Mitchell Krueger (second round)

• # 🇺🇸 Jack Sock (quarterfinals)

• # 🇺🇸 J. J. Wolf (first round)

• # 🇰🇿 Dmitry Popko (first round)

• # 🇺🇸 Bjorn Fratangelo (semifinals)