| Singles | |
|---|---|
| 2017 Heilbronner Neckarcup | |
| Champion |  Filip Krajinović |
| Runner-up |  Norbert Gombos |
| Final score | 6–3, 6–2 |
Nikoloz Basilashvili was the defending champion but chose not to defend his title.
Filip Krajinović won the title after defeating Norbert Gombos 6–3, 6–2 in the final.
Nicolás Kicker (first round)
Evgeny Donskoy (first round)
Adam Pavlásek (first round) Norbert Gombos (final)
Henri Laaksonen (first round) Guido Pella (semifinals) Andrej Martin (quarterfinals)
Casper Ruud (quarterfinals)| Semifinals | Final | ||||||||||||
 Lorenzo Giustino | 3 | 5 | |||||||||||
| 4 | Norbert Gombos | 6 | 7 | ||||||||||
| 4 | Norbert Gombos | 3 | 2 | ||||||||||
| Q | Filip Krajinović | 6 | 6 | ||||||||||
| Q | Filip Krajinović | 4 | 6 | 77 | |||||||||
| 6 | Guido Pella | 6 | 3 | 64 | |||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 1 | N Kicker | 2 | 6 | 1 | |||||||||||||||||||||||
| Q |  D Köpfer | 6 | 3 | 6 | Q | D Köpfer | 64 | 6 | 1 | ||||||||||||||||||
 D Novikov | 4 | 4 | L Giustino | 77 | 1 | 6 | |||||||||||||||||||||
| L Giustino | 6 | 6 | L Giustino | 6 | 7 | ||||||||||||||||||||||
| J Kovalík | 60 | 4 | 7 | A Martin | 3 | 5 | |||||||||||||||||||||
 A Bublik | 77 | 6 | A Bublik | 6 | 3 | 3 | |||||||||||||||||||||
| Q |  S Groth | 3 | 3 | 7 | A Martin | 4 | 6 | 6 | |||||||||||||||||||
| 7 | A Martin | 6 | 6 | L Giustino | 3 | 5 | |||||||||||||||||||||
| 4 | N Gombos | 4 | 77 | 6 | 4 | N Gombos | 6 | 7 | |||||||||||||||||||
| WC | D Brands | 6 | 65 | 3 | 4 | N Gombos | 6 | 6 | |||||||||||||||||||
| WC | D Altmaier | 4 | 4 |  S Diez | 1 | 4 | |||||||||||||||||||||
| S Diez | 6 | 6 | 4 | N Gombos | 6 | 7 | |||||||||||||||||||||
 C Lestienne | 2 | 1 | 8 | C Ruud | 4 | 5 | |||||||||||||||||||||
 M Bašić | 6 | 6 | M Bašić | 5 | 77 | 5 | |||||||||||||||||||||
| WC |  M İlhan | 2 | 6 | 1 | 8 | C Ruud | 7 | 64 | 7 | ||||||||||||||||||
| 8 | C Ruud | 6 | 4 | 6 | |||||||||||||||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 5 | H Laaksonen | 2 | 1 | ||||||||||||||||||||||||
| Q | F Krajinović | 6 | 6 | Q | F Krajinović | 6 | 1 | ||||||||||||||||||||
| T Kamke | 6 | 5 | 77 | T Kamke | 1 | 0r | |||||||||||||||||||||
| S Kozlov | 4 | 7 | 64 | Q | F Krajinović | 77 | 77 | ||||||||||||||||||||
 U Ignatik | 65 | 1 |  M Fucsovics | 62 | 63 | ||||||||||||||||||||||
 K Coppejans | 77 | 6 | K Coppejans | 6 | 3 | 3 | |||||||||||||||||||||
| M Fucsovics | 6 | 7 | M Fucsovics | 3 | 6 | 6 | |||||||||||||||||||||
| 3 | A Pavlásek | 2 | 5 | Q | F Krajinović | 4 | 6 | 77 | |||||||||||||||||||
| 6 | G Pella | 6 | 77 | 6 | G Pella | 6 | 3 | 64 | |||||||||||||||||||
| Q | C-M Stebe | 4 | 62 | 6 | G Pella | 6 | 6 | ||||||||||||||||||||
| WC | Y Maden | 66 | 1 | L Đere | 1 | 0 | |||||||||||||||||||||
| L Đere | 78 | 6 | 6 | G Pella | 6 | 6 | |||||||||||||||||||||
| M Cecchinato | 6 | 6 | M Cecchinato | 2 | 2 | ||||||||||||||||||||||
| D Shapovalov | 3 | 4 | M Cecchinato | 6 | 6 | ||||||||||||||||||||||
| M Krueger | 6 | 4 | 6 | M Krueger | 3 | 2 | |||||||||||||||||||||
| 2 | E Donskoy | 0 | 6 | 4 | |||||||||||||||||||||||
Mikhail Kukushkin was the defending champion but chose to compete in the 2014 Aegon Championships instead.
Kenny de Schepper was the defending champion, but lost in the quarterfinals.
The previous year's runner-up Norbert Gombos won the title, defeating Benoît Paire in the final, 6–1, 7–6(7–4).
Taylor Fritz was the defending champion but chose not to defend his title.
Nick Kyrgios was the defending champion, but lost in the semifinals to Jo-Wilfried Tsonga.
Alexandre Sidorenko was the defending champion but chose not to defend his title.
Thiago Monteiro was the defending champion but chose not to defend his title.
Feliciano López was the champion in 2014, when the men's event was last held, but withdrew before the tournament began.
Pierre-Hugues Herbert was the defending champion but lost in the second round to Illya Marchenko.
Norbert Gombos was the defending champion but lost in the first round to Corentin Moutet.
Norbert Gombos was the defending champion but lost in the first round to Jerzy Janowicz.
Alexander Zverev was the defending champion, but chose not to participate this year.
Jo-Wilfried Tsonga was the defending champion, but withdrew before the tournament began.
Filip Krajinović was the defending champion but chose not to defend his title.
Jason Kubler was the defending champion but chose not to defend his title.
Alexander Zverev was the two-time defending champion but chose not to defend his title.
Stefanos Tsitsipas was the defending champion and successfully defended his title, defeating Félix Auger-Aliassime in the final, 6–3, 6–4.
Dominic Thiem was the defending champion, but lost to Andrey Rublev in the quarterfinals.
Nikoloz Basilashvili defeated Roberto Bautista Agut in the final, 7–6(7–5), 6–2 to win the men's singles tennis title at the 2021 Qatar Open.
Taylor Fritz was the defending champion from when the event was last held in 2019, but withdrew before the tournament with a knee injury.
Mikael Ymer was the defending champion but chose not to defend his title.