Diego Schwartzman defeated Francisco Cerúndolo in the final, 6–1, 6–2 to win the men's singles tennis title at the 2021 Argentina Open.
Casper Ruud was the defending champion,[1] but chose not to participate.
The top four seeds receive a bye into the second round.
Diego Schwartzman (champion)
Cristian Garín (second round)
Benoît Paire (second round)
Miomir Kecmanović (semifinals)
Albert Ramos Viñolas (semifinals) Pablo Andújar (quarterfinals) Laslo Đere (quarterfinals)
Frances Tiafoe (second round) Jaume Munar (qualified)
Hugo Dellien (first round, withdrew)
Daniel Elahi Galán (withdrew)
Thiago Seyboth Wild (second round)
Jozef Kovalík (second round) Francisco Cerúndolo (qualified)
Daniel Altmaier (qualifying competition) Leonardo Mayer (first round)