The MotoGP season will start with two races on successive weekends in Qatar from March 28, followed by Portugal, organisers said on Friday in a calendar re-write forced by the Covid-19 pandemic.
Early season races in Texas and Argentina have been postponed.
The Qatar Grand Prix, a floodlit night race, has long been the opener but will now be followed by a Grand Prix of Doha at the same Losail circuit on April 4.
"The ongoing Covid-19 pandemic and resulting lockdowns and complications sadly oblige the postponement of both the Argentina GP and the Americas GP until the last quarter of 2021," MotoGP said in a statement.
The Argentina round at Termas de Rio Hondo had been scheduled for April 11, with Austin's Circuit of the Americas due to follow a week later, on a provisional 20-race calendar published last November. No new dates were set.
Last year's pandemic-hit season started with two races at Jerez. The southern Spanish track will now host round four on May 2.
Portugal's Algarve circuit near Portimao ended the 2020 season in November and is set for plenty of international action this year, with the World Endurance Championship rescheduling its opener for there and Formula One also expected to return.
Qatar will also host pre-season testing after planned sessions in Malaysia were scrapped, also because of the pandemic.
MotoGP's Qatar race was cancelled last year due to Covid-19 related travel restrictions.
The announcement of the March 28 starting date ended uncertainty about the scheduling of a grand prix that clashes with Formula One's opener on the same evening in nearby Bahrain.
MotoGP indicated that further changes could be made, however.
Indonesia's Mandalika International Street Circuit was listed as reserve venue.
The schedule announced by the FIM finishes in Spain with the Valencia MotoGP on November 14, with five more races planned than in last season's championship won by Suzuki rider Joan Mir.
March 28: Qatar (Losail)
April 4: Qatar (Losail)
April 18: Portugal (Algarve)
May 2: Spain (Jerez)
May 16: France (Le Mans)
May 30: Italy (Mugello)
June 6: Catalonia, Spain (Barcelona)
June 20: Germany (Sachsenring)
June 27: Netherlands (Assen)
July 11: Finland (KymiRing)
August 15: Austria (Spielberg)
August 29: Great Britain (Silverstone)
September 12: Aragon, Spain (Alcaniz)
September 19: San Marino (Misano)
October 3: Japan (Motegi)
October 10: Thailand (Buriram)
October 24: Australia (Phillip Island)
October 31: Malaysia (Sepang)
November 14: Valencia, Spain (Ricardo Tormo)
Postponed GPs, new dates to be confirmed: Argentina (Termas de Río Hondo), United States (Austin)