The 2021 Moselle Open was a tennis tournament played on indoor hard courts. It was the 23rd edition of the Moselle Open, and part of the ATP Tour 250 series of the 2021 ATP Tour. It took place at the Arènes de Metz from 20 September to 26 September 2021.
Champions
Singles
Hubert Hurkacz def. Pablo Carreño Busta 7–6(7–2), 6–3
Doubles
Hubert Hurkacz / Jan Zieliński def. Hugo Nys / Arthur Rinderknech, 7–5, 6–3
Singles main-draw entrants
Seeds
1 Rankings are as of 13 September 2021
Other entrants
The following players received wildcards into the singles main draw: Grégoire Barrère Andy Murray Lucas Pouille
The following player was accepted directly into the main draw using a protected ranking: Gilles Simon
The following player received entry as an alternate: Mikael Ymer
The following players received entry from the qualifying draw: Peter Gojowczyk Alexandre Müller Holger Rune Brayden Schnur
The following players received entry as lucky losers: Antoine Hoang Philipp Kohlschreiber Bernabé Zapata Miralles
Withdrawals
Before the tournament
Carlos Alcaraz → replaced by Marco Cecchinato
Jérémy Chardy → replaced by Mikael Ymer
David Goffin → replaced by Arthur Rinderknech
Yoshihito Nishioka → replaced by Antoine Hoang
Alexei Popyrin → replaced by Bernabé Zapata Miralles
Jannik Sinner → replaced by Philipp Kohlschreiber
Doubles main-draw entrants
Seeds
Rankings are as of 13 September 2021
Other entrants
The following pairs received wildcards into the doubles main draw: Dan Added / Ugo Humbert Grégoire Barrère / Lucas Pouille
The following pair received entry as alternates: Hunter Reese / Sem Verbeek
Withdrawals
Before the tournament
Jérémy Chardy / Łukasz Kubot → replaced by Szymon Walków / Igor Zelenay
Ariel Behar / Gonzalo Escobar → replaced by Marcos Giron / Albano Olivetti
Alejandro Davidovich Fokina / Pedro Martínez → replaced by Hunter Reese / Sem Verbeek Sander Gillé / Joran Vliegen → replaced by Ivan Sabanov / Matej Sabanov Ken Skupski / Neal Skupski → replaced by Matt Reid / Ken Skupski