Joe Joyce will face Joseph Parker in a heavyweight contest on 24 September in Manchester.
Parker and Joyce appeared set to fight in July, the fight even announced, before talks broke down.
But with the fight now agreed Joyce said he believed one more win will secure him a world title shot.
"Parker realised he had nowhere else to go and eventually had to take this fight," Joyce said. "The winner goes on to fight for the world title."
Joyce is ranked number one by the WBO and number two by the WBC. The winner could be announced as mandatory challenger for the heavyweight WBO world title which is currently held by Oleksandr Usyk - the Ukrainian facing Anthony Joshua later this month.
"This is definitely the biggest fight of my career," Joyce told BBC Sport.
"A must-win. It's one of these fights which will cement me as an elite-level fighter and brings me in line to face the winner of AJ-Usyk or maybe even Tyson Fury."
Parker, 30, is a former holder of the WBO title and has just two defeats on his record.
"I have waited patiently to get this fight on and let me tell you now, the Juggernaut's journey ends right here. He has nowhere to run."
'Hardest fight of my career so far'
At 36, Joyce is aware the clock is ticking on his efforts to become a world champion. Joyce is unbeaten in 14 pro fights with an impressive 13 knockouts, but has fought just four times since 2020.
A wrist Injury kept him sidelined at the start of the year and Parker will represent a huge test for the largely untested Olympic silver medallist. Parker may be six years Joyce's junior, but the Kiwi is far more experienced in the professional ranks. Only Joshua and Dillian Whyte have wins over Parker.
"I'm in a great spot. The top of the division. Just a matter of time before I get some proper belts," Joyce insisted.
"It's going to be a tough fight but I can see myself beating Parker. I don't think it will be comfortable.
"It will be challenging the whole way through. He's got good attributes, skill and power as well.
"It's a tough fight but exciting as well because it's one of the hardest fights of my career so far."
How was Joyce v Parker rescued from the 'dead'?
The announcement comes as a shock to boxing fans after weeks of stalled negotiations between Parker and Joyce and their respective teams.
Parker had pencilled in to fight Joyce this summer on BT Sport after agreeing to the bout in April. The fight was even announced during Tyson Fury's heavyweight clash with Dillian Whyte on 23 April.
There was a face-to-face backstage ahead of a July bout, but no contract was officially signed.
Parker then asked for a delay and would go on to sign for rival promoter Boxxer, which is tied to Sky Sports.
Joyce's promoter Frank Warren described the match-up as 'dead' as recently as July, citing there would no chance of a joint-broadcast and that Parker had walked away from the fight. However, it now seems a deal has now been agreed behind the scenes.
"I didn't understand why they thought it couldn't happen just because he'd signed with us," Boxxer's Ben Shalom said at the media conference.
"We put in that offer that Frank didn't react nicely too but hat got us talking. All we wanted to was to make the fight and all Frank wanted to do was make the fight."
BT Sport will broadcast the event, which could produce the next challenger to Usyk's heavyweight titles.
Usyk defends his WBO, IBF and WBA (Super) belts against Joshua on 20 August and if he wins may be ordered by the WBO to fight the winner of Joyce v Parker.
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