2023 Open de Oeiras

Country	Player	Rank1	Seed
FRA	Adrian Mannarino	47	1
FRA	Alexandre Müller	96	2
AUT	Sebastian Ofner	120	3
ARG	Juan Manuel Cerúndolo	123	4
POR	João Sousa	146	5
JPN	Kaichi Uchida	160	6
HUN	Zsombor Piros	167	7
ITA	Andrea Vavassori	176	8

• ¹ Rankings are as of 10 April 2023.^[2]

The following players received wildcards into the singles main draw:

• Henrique Rocha
• Pedro Sousa
• Duarte Vale

The following player received entry into the singles main draw as a special exempt:

• Zsombor Piros

The following player received entry into the singles main draw as an alternate:

• João Domingues

The following players received entry from the qualifying draw:

• Cezar Crețu
• Jaime Faria
• Billy Harris
• Pablo Llamas Ruiz
• Daniel Mérida
• Petr Nouza

The following player received entry as a lucky loser:

• Henri Squire

• Zsombor Piros def. Juan Manuel Cerúndolo 6–3, 6–4.

• Victor Vlad Cornea / Franko Škugor def. Marcelo Demoliner / Andrea Vavassori 7–6^(7–2), 7–6^(7–4).