Kenya's world record holder and Olympic silver medallist Brigid Kosgei will defend her London Marathon title in this year's race on 3 October.
The 27-year-old is aiming for a third successive title in London after also winning the race in 2019.
Ethiopia's Shura Kitata also returns after beating Kenyan great Eliud Kipchoge to win the 2020 men's race.
The event is being run in autumn, rather than its usual April date, because of Covid precautions.
Last year's London Marathon consisted of the elite fields racing on a closed, looped course around St James Park. The mass participation element was done virtually with runners completing the 26.2 miles on a course of their choosing.
This year's edition will involve 50,000 runners completing the traditional course from Blackheath to The Mall.
"It is a great feeling to be coming back, as London is one of my favourite marathons. Last year's win was very special, particularly given what the whole world was going through," said Kosgei.
Kosgei will be up against compatriot and New York champion Joyciline Jepkosgei and Ethiopia's Roza Dereje, the 10th-fastest woman of all time over the distance.
Also in the field is Australia's Sinead Diver, born and raised in Ireland, who finished 10th in the Tokyo Olympic marathon at the age of 44.
Kitata is joined in the men's race by Ethiopian duo Mosinet Geremew and Mule Wasihun, who finished second and third respectively behind Kipchoge in 2019, and Kenya's Evans Chebet, the fastest man in the world this year.
The race comes eight weeks after hot and humid conditions in Sapporo forced Kitata out of the Olympic marathon around six miles in.
"I just did not adapt to the weather well," he said. "It was very cold in Ethiopia prior to leaving for Tokyo and when we got there, the weather took its toll on my body and made my breathing very hard.
"Winning last year was an unforgettable memory and it gave me huge excitement to bring back such a big victory to my country."