2021 Internazionali di Tennis Città di Trieste

Country	Player	Rank1	Seed
BIH	Damir Džumhur	127	1
FRA	Antoine Hoang	143	2
ARG	Tomás Martín Etcheverry	166	3
SRB	Danilo Petrović	173	4
ITA	Alessandro Giannessi	177	5
ARG	Marco Trungelliti	192	6
GER	Maximilian Marterer	196	7
ITA	Thomas Fabbiano	202	8

• ¹ Rankings are as of 19 July 2021.^[1]

The following players received wildcards into the singles main draw:

• Flavio Cobolli
• Robin Haase
• Luca Nardi

The following player received entry into the singles main draw using a protected ranking:

• Julian Lenz

The following players received entry from the qualifying draw:

• Viktor Durasovic
• Pedro Sakamoto
• Timofey Skatov
• Thiago Agustín Tirante

The following player received entry as a lucky loser:

• Orlando Luz

• Tomás Martín Etcheverry def. Thiago Agustín Tirante 6–1, 6–1.

• Orlando Luz / Felipe Meligeni Alves def. Antoine Hoang / Albano Olivetti 7–5, 6–7^(6–8), [10–5].