2021 Knoxville Challenger

The 2021 Knoxville Challenger was a professional tennis tournament played on indoor hard courts. It was the seventeenth edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Knoxville, United States between 8 and 14 November 2021.

Seeds

 * 1 Rankings are as of November 1, 2021.

Other entrants
The following players received wildcards into the singles main draw:
 * 🇺🇸 Aleksandar Kovacevic
 * 🇺🇸 Emilio Nava
 * 🇦🇺 Adam Walton

The following player received entry into the singles main draw using a protected ranking:
 * 🇯🇵 Tatsuma Ito

The following players received entry into the singles main draw as alternates:
 * 🇺🇸 Christian Harrison
 * 🇹🇳 Malek Jaziri
 * 🇨🇦 Peter Polansky

The following players received entry from the qualifying draw:
 * 🇺🇸 JC Aragone
 * Gijs Brouwer
 * 🇬🇧 Aidan McHugh
 * 🇺🇸 Donald Young

Singles

 * 🇺🇸 Christopher Eubanks def. 🇩🇪 Daniel Altmaier 6–3, 6–4.

Doubles

 * 🇹🇳 Malek Jaziri / Blaž Rola def. 🇲🇽 Hans Hach Verdugo / 🇲🇽 Miguel Ángel Reyes-Varela 3–6, 6–3, [10–5].