The Canadian GP has been cancelled for the second successive year due to Covid-19 and will be replaced in its June slot by Turkey.
F1 says that international travel restrictions in Canada meant it "became impossible for Formula 1 to enter the country without a mandatory 14-day quarantine" for the Montreal event.
The Turkish GP at Istanbul Park will instead take over the June 11-13 slot.
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Turkey proved a popular addition to last year's revamped schedule after a nine-year absence from the sport and the November race proved one of the year's most exciting, with Lewis Hamilton clinching his record-equalling seventh world title in the wet.
"While it is disappointing we cannot be in Canada this season we are excited to confirm that Turkey will host a Grand Prix in 2021 after an amazing race last season," said F1 president and CEO Stefano Domenicali.
"I know all our fans are excited by the dramatic start to the season and Turkey is a great circuit that delivers great battles on the track."
As the new seventh round of the season Turkey will now form a more logistically friendly double header with Azerbaijan, which takes place the week before in Baku.
Canada's event at the Circuit Gilles Villeneuve is one of the sport's most long-standing and popular races and, while it will again not take place this year, F1 announced a two-year contract extension on its deal, which now runs to 2031.
"I want to thank the promoter and authorities in Canada for all of their efforts in recent weeks but the travel situation made our plans impossible," said Domenicali.
"I equally want to thank the promoter and authorities in Turkey for their ongoing willingness to host a Formula 1 race that shows the huge interest in our sport and the hope from many locations to have a Grand Prix.
F1 added that it will work with the promoter in Montreal to ensure fans who purchased tickets for the 2020 and 2021 events have the option of a refund or a ticket transfer to 2022's event.
How the 2021 F1 calendar now looks
After unexpectedly completing a total of 17 races - just five fewer than originally planned before the pandemic - as part of a heavily revised calendar in 2020, F1 have a record 23-round schedule in place for this year with plans to return to the Americas and Asia in the final months of the campaign.
"We have had very good conversations will all the other promoters since the start of the year and continue to work closely with them during this period," added Domenicali.
F1 events remain under strict Covid-19 protocols, with the Portuguese GP in the Algarve next up this weekend after dramatic races in Bahrain and Italy.
"The Formula 1 community will continue to travel this season with stringent safety measures that allowed us to travel safely to 12 countries and deliver 17 races 2020," read the F1 statement.
"The measures have proven to be highly effective with over 78,000 Covid-19 tests conducted last season with only 78 positive results, a rate of 0.1%. So far this season we have conducted over 12,000 tests with 14 positive cases again a rate of 0.1%, this is alongside the vaccines that a number of teams have already received and the good rollout of the vaccine in the UK where seven of the ten teams are based.
"We will continue to operate in a way that protects the safety of our personnel and the communities we visit."