The draw was made on Friday with Fiji grouped with champions Australia, Scotland and Italy and New Zealand have been drawn alongside, Lebanon, Jamaica and Ireland.
But the Cook Islands, who have only just qualified for the tournament, are locked in to play what many regard as the 'group of death'.
The Kukis go up against the remarkable Tongans, who most recently upset Australia, Papua New Guinea and Wales.
Cook Islands coach Tony Iro said his team was excited at the prospect of playing top teams.
"Obviously, Tonga will be the favourites but we're looking forward to the challenge against a Papua New Guinea team that's really improved over the last two years.
"Wales they're probably on a bit of a down turn but there is still a year and a half to go until the tournament so anything could happen," he said.
Iro said although it was a tough group, the team was ready to show the world what they were made of.
We're going to have a couple of tough games and it's a tough pool but I think if we can get our right squad together and play well, then we've got as much chance as anyone else in that group."
Iro said his team, like everyone else, will be aiming to make the quarterfinals of the tournament.
Tony Iro, who represented both New Zealand and the Cook Islands internationally, said his team would get the opportunity to kick off their world cup preparation with their promotion this year's Oceania Cup.
The Cook Islands will play in Group B of the Cup alongside Samoa and PNG.
With Australia not taking part in the Oceania Cup due to their northern tour, Fiji has been promoted into Group A with Tonga and New Zealand and the Cook Island were given their slot.
"We've got an opportunity this year to play in the Oceania Cup which gives us a couple of games against some quality opposition including fellow [RLWC 2021] pool members in Papua New Guinea," Iro said.
"It's going to be a good opportunity for us to test ourselves against some quality opposition and to get the team together...so we can improve as a unit before the tournament proper."
The women's RLWC 2021 is set to run concurrently to the men's for the first time with PNG joining England, Canada and Brazil in Group A, and the Cook Islands booked in with New Zealand, Australia and France.
"The women's pool is looking really exciting with the ladies going up against New Zealand and Australia. I'm really looking forward to it," Iro said.
He expected the entire Cook Islands to get behind the teams.
"The Cook Island population and people are really excited about it.
"There's going to be a fairly big contingent going over [in England] and the fact that it's still a year and a half away still gives people plenty of time to plan so we're looking forward to a lot of support over there."
Fixtures dates for the tournament are yet to be announced but English Premier League football grounds like Old Trafford, Anfield, and the Emirates Stadium are among the 18 venues to be used.