| Singles | |
|---|---|
| 2018 Karshi Challenger | |
| Champion |  Egor Gerasimov |
| Runner-up | Sergey Betov |
| Final score | 7–6(7–3), 2–0 ret. |
Egor Gerasimov was the defending champion and successfully defended his title.
Gerasimov won the title after Sergey Betov retired trailing 6–7(3–7), 0–2 in the final.
Hubert Hurkacz (first round, retired)
Nikola Milojević (second round) Egor Gerasimov (champion) Uladzimir Ignatik (quarterfinals)
Aleksandr Nedovyesov (second round, retired)
Lloyd Harris (quarterfinals)
Aldin Šetkić (second round)
Yang Tsung-hua (second round)| Semifinals | Final | ||||||||||||
 Carlos Boluda-Purkiss | 63 | 1 | |||||||||||
| Q | Sergey Betov | 77 | 6 | ||||||||||
| Q | Sergey Betov | 63 | 0r | ||||||||||
| 3 | Egor Gerasimov | 77 | 2 | ||||||||||
| 3 | Egor Gerasimov | 77 | 77 | ||||||||||
 Cem İlkel | 64 | 64 | |||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 1 | H Hurkacz | 66 | 2r | ||||||||||||||||||||||||
| M Vilella Martínez | 78 | 5 | M Vilella Martínez | 1 | 5 | ||||||||||||||||||||||
 K Kravchuk | 63 | 3 | WC |  K Sultanov | 6 | 7 | |||||||||||||||||||||
| WC | K Sultanov | 77 | 6 | WC | K Sultanov | 63 | 4 | ||||||||||||||||||||
| E Tyurnev | 5 | 6 | 2 | C Boluda-Purkiss | 77 | 6 | |||||||||||||||||||||
| Carlos Boluda-Purkiss | 7 | 3 | 6 | C Boluda-Purkiss | 6 | 5 | 79 | ||||||||||||||||||||
 A Bega | 4 | 4 | 8 | T-h Yang | 4 | 7 | 67 | ||||||||||||||||||||
| 8 | T-h Yang | 6 | 6 | C Boluda-Purkiss | 63 | 1 | |||||||||||||||||||||
| 4 | U Ignatik | 6 | 6 | Q | S Betov | 77 | 6 | ||||||||||||||||||||
| WC | S Fomin | 3 | 3 | 4 | U Ignatik | 6 | 6 | ||||||||||||||||||||
 K Uchida | 1 | 6 | 6 | K Uchida | 3 | 3 | |||||||||||||||||||||
| H Moriya | 6 | 2 | 3 | 4 | U Ignatik | 3 | 61 | ||||||||||||||||||||
| WC | J Karimov | 64 | 3 | Q | S Betov | 6 | 77 | ||||||||||||||||||||
| Q | S Betov | 77 | 6 | Q | S Betov | 6 | 4 | 77 | |||||||||||||||||||
| Q | Shuichi Sekiguchi | 1 | 5 | 7 | A Šetkić | 4 | 6 | 64 | |||||||||||||||||||
| 7 | A Šetkić | 6 | 7 | ||||||||||||||||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 6 | L Harris | 77 | 1 | 6 | |||||||||||||||||||||||
| I Gakhov | 65 | 6 | 3 | 6 | L Harris | 3 | 77 | 6 | |||||||||||||||||||
| R Ortega Olmedo | 77 | 6 | R Ortega Olmedo | 6 | 64 | 3 | |||||||||||||||||||||
| Q |  T Lamasine | 63 | 4 | 6 | L Harris | 1 | 6 | 3 | |||||||||||||||||||
| T Gabashvili | 6 | 6 | 3 | E Gerasimov | 6 | 3 | 6 | ||||||||||||||||||||
 JC Aragone | 2 | 4 | T Gabashvili | 4 | 65 | ||||||||||||||||||||||
| WC | F Dustov | 3 | 4 | 3 | E Gerasimov | 6 | 77 | ||||||||||||||||||||
| 3 | E Gerasimov | 6 | 6 | 3 | E Gerasimov | 77 | 77 | ||||||||||||||||||||
| 5 | A Nedovyesov | 77 | 7 | C İlkel | 64 | 64 | |||||||||||||||||||||
| A Basso | 65 | 5 | 5 | A Nedovyesov | 6 | 3 | 0r | ||||||||||||||||||||
| C İlkel | 6 | 77 | C İlkel | 3 | 6 | 4 | |||||||||||||||||||||
| Jared Hiltzik | 2 | 64 | C İlkel | 3 | 6 | 6 | |||||||||||||||||||||
| S Fayziev | 6 | 2 | 64 | Q |  S Mukund | 6 | 2 | 3 | |||||||||||||||||||
| Q | S Mukund | 4 | 6 | 77 | Q | S Mukund | 6 | 0 | 6 | ||||||||||||||||||
| R Safiullin | 4 | 2 | 2 | N Milojević | 3 | 6 | 2 | ||||||||||||||||||||
| 2 | N Milojević | 6 | 6 | ||||||||||||||||||||||||
Radu Albot was the defending champion but decided to participate at the 2014 Košice Open instead.
Alexandre Sidorenko was the defending champion but chose not to defend his title.
Illya Marchenko was the defending champion but chose not to defend his title.
Evgeny Donskoy was the defending champion but lost in the quarterfinals to Egor Gerasimov.
Florian Mayer was the defending champion but chose not to defend his title.
Damir Džumhur was the defending champion, but lost to Egor Gerasimov in the first round.
Mirza Bašić was the defending champion but lost in the first round to Martin Kližan.
Karen Khachanov was the defending champion, but withdrew before the tournament began.
Marco Cecchinato was the defending champion, but withdrew due to illness.
João Sousa was the defending champion, but lost in the second round to David Goffin.
Daniel Brands was the defending champion but chose not to defend his title.
Fabio Fognini was the defending champion, but lost in the quarterfinals to Taylor Fritz.
Thanasi Kokkinakis was the defending champion but lost in the second round to Egor Gerasimov.
Dominic Thiem was the defending champion, but chose to compete in the Laver Cup instead.
Karen Khachanov was the defending champion, but lost in the quarterfinals to Andreas Seppi.
Stefanos Tsitsipas was the defending champion and successfully defended his title, defeating Félix Auger-Aliassime in the final, 6–3, 6–4.
Jannik Sinner was the defending champion and successfully defended his title, defeating Gaël Monfils in the final, 6–3, 6–4.
Andrey Rublev was the defending champion, but lost in the quarterfinals to Botic van de Zandschulp.
Tommy Paul defeated the defending champion, Denis Shapovalov, in the final, 6–4, 2–6, 6–4, to win the singles title at the 2021 Stockholm Open. This was Paul's first ATP Tour title.
Félix Auger-Aliassime defeated Stefanos Tsitsipas in the final, 6–4, 6–2. It was his maiden ATP Tour title, following eight runner-up finishes in prior finals.