| 2021 Open de Oeiras II | |
|---|---|
| Date | 5–11 April |
| Edition | 2nd |
| Surface | Clay |
| Location | Oeiras, Portugal |
| Champions | |
| Singles | |
 Pedro Cachin | |
| Doubles | |
 Nuno Borges / Francisco Cabral | |
The 2021 Open de Oeiras II was a professional tennis tournament played on clay courts. It was the second edition of the tournament, part of the 2021 ATP Challenger Tour. It took place in Oeiras, Portugal between 5 and 11 April 2021.
| Country | Player | Rank1 | Seed |
|---|---|---|---|
 GER | Oscar Otte | 154 | 1 |
 FRA | Enzo Couacaud | 185 | 2 |
 USA | Ernesto Escobedo | 205 | 3 |
 MAR | Elliot Benchetrit | 240 | 4 |
 ITA | Gian Marco Moroni | 241 | 5 |
| ARG | Marco Trungelliti | 247 | 6 |
 ESP | Nicola Kuhn | 250 | 7 |
| FRA | Tristan Lamasine | 257 | 8 |
The following players received wildcards into the singles main draw:
Pedro Araújo Nuno Borges Tiago Cação The following player received entry into the singles main draw as a special exempt:
The following players received entry into the singles main draw as alternates:
The following players received entry from the qualifying draw:
Pedro Cachin def. Nuno Borges 7–6(7–4), 7–6(7–3). Nuno Borges / Francisco Cabral def. 
Pavel Kotov / 
Tseng Chun-hsin 6–1, 6–2.
Pedro Cachin is an Argentine professional tennis player. Cachin has a career high ATP singles ranking of world No. 54 achieved on 14 November 2022. He also has a career high ATP doubles ranking of world No. 219 achieved on 9 May 2022. Cachin had a career high Junior ranking of No. 8 achieved on 9 December 2013.
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