2021 Monte-Carlo Masters – Singles

Stefanos Tsitsipas defeated Andrey Rublev in the final, 6–3, 6–3 to win the singles tennis title at the 2021 Monte-Carlo Masters. It was his first ATP Tour Masters 1000 title, making him the first Greek to win a Masters tournament. Rublev was also in contention for his maiden Masters 1000 title.

Fabio Fognini was the defending champion from when the tournament was last held in 2019, but lost to Casper Ruud in the quarterfinals.

Seeds
The top eight seeds received a bye into the second round. • 🇷🇸 Novak Djokovic (third round)

• 🇷🇺 Daniil Medvedev (withdrew, tested positive for COVID-19)

• 🇪🇸 Rafael Nadal (quarterfinals)

• Stefanos Tsitsipas (champion)

• 🇩🇪 Alexander Zverev (third round)

• 🇷🇺 Andrey Rublev (final)

• 🇦🇷 Diego Schwartzman (second round)

• 🇮🇹 Matteo Berrettini (second round)

• 🇪🇸 Roberto Bautista Agut (third round)

• 🇫🇷 Gaël Monfils (withdrew)

• 🇧🇪 David Goffin (quarterfinals)

• 🇪🇸 Pablo Carreño Busta (third round)

• 🇵🇱 Hubert Hurkacz (second round)

• 🇧🇬 Grigor Dimitrov (third round)

• 🇮🇹 Fabio Fognini (quarterfinals)

•  Cristian Garín (third round)

Seeds
• # 🇩🇪 Dominik Koepfer (qualified)

• # 🇮🇹 Stefano Travaglia (qualified)

• # 🇨🇿 Jiří Veselý (first round)

• # 🇫🇷 Pierre-Hugues Herbert (first round)

• # 🇫🇷 Corentin Moutet (first round)

• # 🇧🇷 Thiago Monteiro (first round)

• # 🇧🇾 Egor Gerasimov (first round)

• # 🇦🇺 Alexei Popyrin (qualified)

• # 🇦🇷 Federico Delbonis (qualified)

• # 🇦🇷 Federico Coria (first round)

• # 🇮🇹 Salvatore Caruso (qualified)

• # 🇮🇹 Gianluca Mager (first round)

• # 🇮🇹 Marco Cecchinato (qualified)

• # 🇦🇷 Juan Ignacio Londero (qualifying competition, lucky loser)

Qualifiers
• # 🇩🇪 Dominik Koepfer

• # 🇮🇹 Stefano Travaglia

• # 🇦🇺 Alexei Popyrin

• # 🇮🇹 Salvatore Caruso

• # 🇦🇷 Federico Delbonis

• # 🇮🇹 Thomas Fabbiano

• # 🇮🇹 Marco Cecchinato

Lucky losers
• # 🇪🇸 Pedro Martínez

• # 🇦🇷 Juan Ignacio Londero