Portugal will fill a slot left vacant by Vietnam and be the third race of the Formula One season on May 2, the sport confirmed on Friday.
The race will again be held at the Algarve circuit near Portimao that made its debut last October on a calendar reduced to 17 races as a result of cancellations due to the COVID-19 pandemic.
That was the first Portuguese Grand Prix in 25 years.
Formula One is planning a record 23 races this year, with the season starting on March 28 in Bahrain.
"We want to thank the promoter and the Portuguese Government for their hard work and dedication in getting us to this point," said Formula One chief executive Stefano Domenicali in a statement.
"We are confident and excited about our 2021 season, having shown last year that we could deliver 17 races safely and bring our millions of fans thrilling racing at a difficult time.
"We hope to welcome fans to Portimao again this season in a safe way and are working with the promoter on the details of that plan."