| Date: | 3–9 May 2021 |
| Edition: | 28th (men) 16th (women) |
| Surface: | Clay |
| Location: | Prague, Czech Republic |
| Prize Money: | €44,820 (men) $25,000 (women) |
| Champms: | Tallon Griekspoor |
| Champws: | Jule Niemeier |
| Champmd: |  Marc Polmans /  Sergiy Stakhovsky |
| Champwd: |  Anna Bondár /  Kimberley Zimmermann |
| Before Name: | I.ČLTK Prague Open |
The 2021 I.ČLTK Prague Open was a professional tennis tournament played on outdoor clay courts. It was the 28th (men) and 16th (women) editions of the tournament which was part of the 2021 ATP Challenger Tour and the 2021 ITF Women's World Tennis Tour. It took place in Prague, Czech Republic from 3 to 9 May 2021.
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
 Slovakia | Norbert Gombos | 95 | 1 | |
 Japan | Yūichi Sugita | 109 | 2 | |
| Slovakia | Andrej Martin | 110 | 3 | |
 Austria | Dennis Novak | 111 | 4 | |
| Denis Kudla | 117 | 5 | ||
 Poland | Kamil Majchrzak | 123 | 6 | |
| Peter Gojowczyk | 132 | 7 | ||
 India | Sumit Nagal | 137 | 8 |
The following players received wildcards into the singles main draw:
The following player received entry into the singles main draw as a special exempt:
The following players received entry from the qualifying draw:
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
| Slovakia | Viktória Kužmová | 106 | 1 | |
 Romania | Jaqueline Cristian | 147 | 2 | |
| Austria | Barbara Haas | 156 | 3 | |
| Romania | Elena-Gabriela Ruse | 175 | 4 | |
 Turkey | Çağla Büyükakçay | 177 | 5 | |
| Lesley Pattinama Kerkhove | 179 | 6 | ||
| Slovakia | Rebecca Šramková | 196 | 7 | |
| Austria | Julia Grabher | 197 | 8 |
The following players received wildcards into the singles main draw:
The following player received entry using a protected ranking:
The following players received entry from the qualifying draw:
Anna Bondár
Amanda Carreras
Johana Marková
Paula Ormaechea İpek Öz Chantal Škamlová
Shalimar TalbiSee main article: 2021 I.ČLTK Prague Open – Men's singles.
Dalma Gálfi, 6–4, 6–2See main article: 2021 I.ČLTK Prague Open – Men's doubles.
Marc Polmans / Sergiy Stakhovsky def. Ivan Sabanov / Matej Sabanov 6–3, 6–4. Anna Bondár / Kimberley Zimmermann def. Xenia Knoll / Elena-Gabriela Ruse, 7–6(7–5), 6–2