| Singles | |
|---|---|
| 2018 Lyon Open | |
| Champion |  Dominic Thiem |
| Runner-up |  Gilles Simon |
| Final score | 3–6, 7–6(7–2), 6–1 |
| Draw | 28 (4 Q / 3 WC ) |
| Seeds | 8 |
Jo-Wilfried Tsonga was the defending champion, but due to injury did not defend his title.
Dominic Thiem won the title, defeating Gilles Simon in the final, 3–6, 7–6(7–2), 6–1.
The top four seeds receive a bye into the second round.
Dominic Thiem (Champion)
John Isner (Quarterfinals) Jack Sock (Second round)
Chung Hyeon (Withdrew) Adrian Mannarino (First round) Gaël Monfils (First round)
João Sousa (First round)
John Millman (Withdrew)| Semifinals | Final | ||||||||||||
| 1 | Dominic Thiem | 6 | 5 | 6 | |||||||||
 Dušan Lajović | 4 | 7 | 4 | ||||||||||
| 1 | Dominic Thiem | 3 | 77 | 6 | |||||||||
| Gilles Simon | 6 | 62 | 1 | ||||||||||
| Gilles Simon | 6 | 78 | |||||||||||
 Cameron Norrie | 1 | 66 | |||||||||||
| First Round | Second Round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 1 | D Thiem | 6 | 6 | ||||||||||||||||||||||||
 R Carballés Baena | 77 | 64 | 6 | R Carballés Baena | 2 | 4 | |||||||||||||||||||||
| Q | L Đere | 63 | 77 | 3 | 1 | D Thiem | 64 | 77 | 6 | ||||||||||||||||||
| WC | C Moutet | 77 | 4 | 3 | G García López | 77 | 60 | 4 | |||||||||||||||||||
| C Hemery | 64 | 6 | 6 | C Hemery | 64 | 3 | |||||||||||||||||||||
| G García López | 6 | 4 | 6 | G García López | 77 | 6 | |||||||||||||||||||||
| 5/WC | A Mannarino | 3 | 6 | 1 | 1 | D Thiem | 6 | 5 | 6 | ||||||||||||||||||
| D Lajović | 4 | 7 | 4 | ||||||||||||||||||||||||
| 3 | J Sock | 66 | 2 | ||||||||||||||||||||||||
| T Fritz | 6 | 6 | T Fritz | 78 | 6 | ||||||||||||||||||||||
| M Ebden | 4 | 2 | T Fritz | 5 | 1 | ||||||||||||||||||||||
| D Lajović | 6 | 6 | D Lajović | 7 | 6 | ||||||||||||||||||||||
 H Zeballos | 4 | 2 | D Lajović | 6 | 7 | ||||||||||||||||||||||
| Q |  F Horanský | 6 | 3 | 6 | Q | F Horanský | 4 | 5 | |||||||||||||||||||
| 7 | J Sousa | 4 | 6 | 4 | |||||||||||||||||||||||
| First Round | Second Round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| LL | F Coria | 4 | 6 | 7 | |||||||||||||||||||||||
| N Kicker | 6 | 1 | 5 | LL | F Coria | 2 | 3 | ||||||||||||||||||||
| WC | G Barrère | 2 | 3 |  M Kukushkin | 6 | 6 | |||||||||||||||||||||
| M Kukushkin | 6 | 6 | M Kukushkin | 6 | 4 | 65 | |||||||||||||||||||||
| G Simon | 6 | 6 | G Simon | 4 | 6 | 77 | |||||||||||||||||||||
| Q | J Samper-Montaña | 4 | 2 | G Simon | 77 | 6 | |||||||||||||||||||||
| LL |  J De Loore | 63 | 2 | ||||||||||||||||||||||||
| G Simon | 6 | 78 | |||||||||||||||||||||||||
| 6 | G Monfils | 6 | 4 | 4 | C Norrie | 1 | 66 | ||||||||||||||||||||
 M Marterer | 2 | 6 | 6 | M Marterer | 1 | 4 | |||||||||||||||||||||
| C Norrie | 77 | 6 | C Norrie | 6 | 6 | ||||||||||||||||||||||
| Q |  J Hernández-Fernández | 65 | 1 | C Norrie | 77 | 6 | |||||||||||||||||||||
| F Delbonis | 79 | 5 | 4 | 2 | J Isner | 61 | 4 | ||||||||||||||||||||
 R Albot | 67 | 7 | 6 | R Albot | 63 | 3 | |||||||||||||||||||||
| 2 | J Isner | 77 | 6 | ||||||||||||||||||||||||
Laslo Đere (Qualified)
Roberto Quiroz (First round) José Hernández-Fernández (Qualified)
Alejandro González (First round) Maxime Janvier (First round)
Steven Diez (First round) Federico Coria (Qualifying competition, Lucky loser)
Evgeny Karlovskiy (First round)| First Round | Qualifying Competition | ||||||||||||
| 1 | Laslo Đere | 6 | 6 | ||||||||||
| Yannick Mertens | 4 | 3 | |||||||||||
| 1 | Laslo Đere | 7 | 6 | ||||||||||
| Joris De Loore | 5 | 4 | |||||||||||
| Joris De Loore | 4 | 6 | 7 | ||||||||||
| 5 | Maxime Janvier | 6 | 3 | 5 | |||||||||
| First Round | Qualifying Competition | ||||||||||||
| 2 | Roberto Quiroz | 4 | 2 | ||||||||||
| Filip Horanský | 6 | 6 | |||||||||||
| Filip Horanský | 6 | 6 | |||||||||||
| WC | Antoine Cornut Chauvinc | 1 | 3 | ||||||||||
| WC | Antoine Cornut Chauvinc | 5 | 6 | 6 | |||||||||
| 6 | Steven Diez | 7 | 2 | 1 | |||||||||
| First Round | Qualifying Competition | ||||||||||||
| 3 | José Hernández-Fernández | 77 | 6 | ||||||||||
| Tristan Lamasine | 62 | 4 | |||||||||||
| 3 | José Hernández-Fernández | 6 | 6 | ||||||||||
| 7 | Federico Coria | 2 | 4 | ||||||||||
| Axel Michon | 3 | 0 | |||||||||||
| 7 | Federico Coria | 6 | 6 | ||||||||||
| First Round | Qualifying Competition | ||||||||||||
| 4 | Alejandro González | 6 | 3 | 5 | |||||||||
| Jordi Samper-Montaña | 3 | 6 | 7 | ||||||||||
| Jordi Samper-Montaña | 6 | 4 | 6 | ||||||||||
| WC | Matteo Martineau | 3 | 6 | 3 | |||||||||
| WC | Matteo Martineau | 6 | 3 | 6 | |||||||||
| 8 | Evgeny Karlovskiy | 3 | 6 | 3 | |||||||||
Pablo Cuevas was the defending champion, but he chose to defend his title in Båstad instead.
Federico Gaio was the defending champion but lost in the second round to Federico Coria.
Martin Kližan was the defending champion, but withdrew before the tournament began.
Roberto Bautista Agut was the defending champion, but withdrew before the tournament began.
Diego Schwartzman was the defending champion, but he retired in the first round against Pablo Cuevas.
Juan Martín del Potro was the defending champion, but withdrew due to a knee injury before the tournament began.
Rafael Nadal was the three-time defending champion, but lost in the semifinals to Dominic Thiem.
Marco Cecchinato was the defending champion, but withdrew due to illness.
Nikoloz Basilashvili was the defending champion and successfully defended his title, defeating Andrey Rublev in the final, 7–5, 4–6, 6–3. En route to doing so, Basilashvili saved two match points against Alexander Zverev in the semifinals.
Kevin Anderson was the defending champion, but could not participate this year due to a knee injury.
Juan Ignacio Londero was the defending champion, but lost to Laslo Đere in the quarterfinals.
Marco Cecchinato was the defending champion, but lost in the first round to Roberto Carballés Baena.
Laslo Đere was the defending champion, but withdrew with an abdominal injury before the tournament began.
Daniil Medvedev was the defending champion, but lost in the quarterfinals to Roberto Bautista Agut.
Dominic Thiem was the defending champion and chose not to defend his title, as he was still competing at the 2020 US Open.
This was the first edition of the tournament, primarily organised due to the cancellation of many tournaments in 2020, due to the COVID-19 pandemic.
Novak Djokovic was the defending champion, but he chose not to participate this year.
Cristian Garín defeated Facundo Bagnis in the final, 6–4, 6–7(3–7), 7–5 to capture the Men's Singles tennis title at the 2021 Chile Open.
Alexander Zverev defeated Matteo Berrettini in the final, 6–7(8–10), 6–4, 6–3 to win the Men's Singles tennis title at the 2021 Madrid Open.
Rafael Nadal defeated defending champion Novak Djokovic in the final 7–5, 1–6, 6–3 to win his 10th Men's Singles tennis title at the 2021 Italian Open. This was Nadal's 36th Masters 1000 title, tying Djokovic in first place for most Masters tournaments won. Nadal had saved 2 match points in his third round match against Denis Shapovalov. This marks the fourth time that Nadal has won a tournament on 10 or more occasions, the only tennis player to do so.