# 2021 Singapore Tennis Open – Singles

Alexei Popyrin defeated Alexander Bublik 4–6, 6–0, 6–2 to claim his first ATP Tour Men's Singles tennis title at the 2021 Singapore Open. The Singapore Tennis Open was a new addition to the ATP Tour in 2021

## Seeds

The top four seeds receive a bye into the second round.
* Adrian Mannarino (quarterfinals)
* John Millman (second round)
* Marin Čilić (semifinals)
* Alexander Bublik (final)
* Yoshihito Nishioka (quarterfinals)
* Radu Albot (semifinals)
* Lloyd Harris (first round)
* Kwon Soon-woo (quarterfinals)

## Draw
### Key

* Q = Qualifier
* WC = Wild card
* LL = Lucky loser
* Alt = Alternate
* SE = Special exempt
* PR = Protected ranking
* ITF = ITF entry
* JE = Junior exempt
* w/o = Walkover
* r = Retired
* d = Defaulted
* SR = Special ranking

### Finals

| Semifinals | Semifinals | Semifinals | Semifinals | Semifinals | Final | Final | Final | Final | Final |
| 6 | Radu Albot | 6 | 3 | 4 | | | | | |
| 4 | Alexander Bublik | 2 | 6 | 6 | | | | | |
| 4 | Alexander Bublik | 2 | 6 | 6 | 4 | Alexander Bublik | 6 | 0 | 2 |
| | | | | | | Alexei Popyrin | 4 | 6 | 6 |
| 3 | Marin Čilić | 6$^5$ | 6$^2$ | | | Alexei Popyrin | 4 | 6 | 6 |
| | Alexei Popyrin | 7$^7$ | 7$^7$ | | | | | | |

### Top half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals | Semifinals |
| | | | | | 1 | A Mannarino | 6 | 7 | | | | | | | | | | |
| | R Marcora | 7 | 6 | | | R Marcora | 3 | 5 | | | | | | | | | | |
| | E Gulbis | 5 | 4 | | | | | | | 1 | A Mannarino | 3 | 4 | | | | | |
| | J Duckworth | 2 | 4 | | | | | | | 6 | R Albot | 6 | 6 | | | | | |
| | Y Hanfmann | 6 | 6 | | | Y Hanfmann | 7$^7$ | 6$^7$ | 3 | | | | | | | | | |
| Q | J-P Smith | 2 | 6 | 1 | 6 | R Albot | 6$^2$ | 7$^9$ | 6 | | | | | | | | | |
| 6 | R Albot | 6 | 3 | 6 | | | | | | | | | | 6 | R Albot | 6 | 3 | 4 |
| | | | | | | | | | | | | | | 4 | A Bublik | 2 | 6 | 6 |
| | | | | | 4 | A Bublik | 6 | 6 | | | | | | | | | | |
| WC | S Mochizuki | 0 | 4 | | Q | A Çelikbilek | 2 | 2 | | | | | | | | | | |
| Q | A Çelikbilek | 6 | 6 | | | | | | | 4 | A Bublik | 6 | 6 | | | | | |
| | J Jung | 6$^4$ | 2 | | | | | | | 5 | Y Nishioka | 3 | 2 | | | | | |
| | M Cressy | 7$^7$ | 6 | | | M Cressy | 4 | 2 | | | | | | | | | | |
| | M Mmoh | 2 | 6 | 3 | 5 | Y Nishioka | 6 | 6 | | | | | | | | | | |
| 5 | Y Nishioka | 6 | 3 | 6 | | | | | | | | | | | | | | |

### Bottom half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 8 | S-w Kwon | 4 | 6 | 6 | | | | | | | | | | | | | | |
| Q | T-S Kwiatkowski | 6 | 3 | 4 | 8 | S-w Kwon | 6 | 6 | | | | | | | | | | |
| | Y Uchiyama | 6 | 2 | 6 | | Y Uchiyama | 3 | 4 | | | | | | | | | | |
| | M Polmans | 4 | 6 | 4 | | | | | | 8 | S-w Kwon | 2 | 6 | 5 | | | | |
| | T Daniel | 6 | 6$^3$ | 6 | | | | | | 3 | M Čilić | 6 | 2 | 7 | | | | |
| | R Ramanathan | 3 | 7$^7$ | 3 | | T Daniel | 5 | 4 | | | | | | | | | | |
| | | | | | 3 | M Čilić | 7 | 6 | | | | | | | | | | |
| | | | | | | | | | | | | | | | 3 | M Čilić | 6$^5$ | 6$^2$ |
| 7 | L Harris | 6 | 3 | 4 | | | | | | | | | | | | A Popyrin | 7$^7$ | 7$^7$ |
| WC | A Andreev | 1 | 6 | 6 | WC | A Andreev | 1 | 7 | 3 | | | | | | | | | |
| Q | C Eubanks | 6$^5$ | 6$^5$ | | | A Popyrin | 6 | 5 | 6 | | | | | | | | | |
| | A Popyrin | 7$^7$ | 7$^7$ | | | | | | | | A Popyrin | 6 | 7$^9$ | | | | | |
| PR | Y Bhambri | 3 | 6$^3$ | | | | | | | WC | M Ebden | 4 | 6$^7$ | | | | | |
| WC | M Ebden | 6 | 7$^7$ | | WC | M Ebden | 6 | 6 | | | | | | | | | | |
| | | | | | 2 | J Millman | 4 | 1 | | | | | | | | | | |

## Qualifying
### Seeds

* Thai-Son Kwiatkowski (qualified)
* Matteo Viola (qualifying competition)
* Christopher Eubanks (qualified)
* Malek Jaziri (qualifying competition)
* Altuğ Çelikbilek (qualified)
* John-Patrick Smith (qualified)
* Alessandro Bega (qualifying competition)
* Vladyslav Orlov (first round)

### Qualifiers

* Thai-Son Kwiatkowski
* Altuğ Çelikbilek
* Christopher Eubanks
* John-Patrick Smith

### Qualifying draw
#### First qualifier

| First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 1 | Thai-Son Kwiatkowski | 6 | 7$^7$ | | | | |
| Alt | Luke Bambridge | 4 | 6$^4$ | | | | |
| Alt | Luke Bambridge | 4 | 6$^4$ | 1 | Thai-Son Kwiatkowski | 6 | 6 |
| | | | | Alt | Robert Galloway | 2 | 3 |
| Alt | Robert Galloway | 6 | 6 | Alt | Robert Galloway | 2 | 3 |
| 8 | Vladyslav Orlov | 4 | 4 | | | | |

#### Second qualifier

| First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 2 | Matteo Viola | 6 | 6 | | | | | |
| Alt | Alex Lawson | 3 | 2 | | | | | |
| Alt | Alex Lawson | 3 | 2 | 2 | Matteo Viola | 2 | 6 | 6$^5$ |
| | | | | 5 | Altuğ Çelikbilek | 6 | 0 | 7$^7$ |
| | Evan King | 2 | 4 | 5 | Altuğ Çelikbilek | 6 | 0 | 7$^7$ |
| 5 | Altuğ Çelikbilek | 6 | 6 | | | | | |

#### Third qualifier

| First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 3 | Christopher Eubanks | 6 | 6 | | | | |
| Alt | Rohan Bopanna | 3 | 4 | | | | |
| Alt | Rohan Bopanna | 3 | 4 | 3 | Christopher Eubanks | 6 | 6 |
| | | | | 7 | Alessandro Bega | 1 | 2 |
| | Fabrizio Ornago | 5 | 2 | 7 | Alessandro Bega | 1 | 2 |
| 7 | Alessandro Bega | 7 | 6 | | | | |

#### Fourth qualifier

| First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 4 | Malek Jaziri | 6 | 6 | | | | |
| WC | Shaheed Alam | 1 | 3 | | | | |
| WC | Shaheed Alam | 1 | 3 | 4 | Malek Jaziri | 5 | 6$^5$ |
| | | | | 6 | John-Patrick Smith | 7 | 7$^7$ |
| WC | Roy Hobbs | 1 | 1 | 6 | John-Patrick Smith | 7 | 7$^7$ |
| 6 | John-Patrick Smith | 6 | 6 | | | | |