Race director Hugh Brasher expects "the most memorable London Marathon ever" as the mass participation event returns to its traditional course for the first time in more than two years.
Only the elite races took place in 2020 because of Covid-19 restrictions, with amateurs last competing in April 2019.
More than 40,000 will take to London's streets on Sunday, with a further 40,000 participating virtually.
"It will be a moment of joy, of true emotion," Brasher told BBC Breakfast.
"Something we think could easily be the most memorable London Marathon ever."
As well as the return of mass participants after they competed virtually in 2020, there will be several changes to the event because of the pandemic as well as the organisers' drive to make the race more sustainable.
All runners must show a negative Covid-19 lateral flow test and are being encouraged to only bring one supporter in order to avoid crowds.
Elite athletes will be subject to regular PCR tests and the start will be staggered in an attempt to spread out mass participants.
"It is more than just a marathon," Brasher continued "This is about bringing people together and that is what we have missed so much in the last 18 months.
"The attack on our mental health, our physical health from being constrained has been huge.
"Getting people together outdoors in a safe environment in the way that we have organised the event - that is so good for people and that is what we want to celebrate on Sunday."
Some of the measures introduced to reduce the race's environmental impact include using kitbags made from sugar cane instead of plastic, electric vehicles at the head of the race, and collecting waste to make mile markers for future events.
Change could be imminent in terms of who televises the marathon, with Brasher in negotiations with broadcasters about a future deal.
The BBC has shown the event for four decades.
"We've had an amazing partnership with the BBC for the last 40 years," Brasher said.
"The BBC has helped make this event what it is, which is truly an event for people. We obviously are talking to broadcasters. It is something that should be on terrestrial TV."