Aymeric Laporte on Monday announced he was leaving Athletic Bilbao with Premier League leaders Manchester City primed to break their transfer record to sign the French defender.
Bilbao posted a leaving message from Laporte on their Twitter feed, saying his 65 million euros ($80 million) release clause had been paid.
It means Pep Guardiola's City are set to surpass the £55 million they paid for Belgium attacking midfielder Kevin de Bruyne -- Laporte's transfer fee translates as £57 million.
The 23-year-old will also become the second most expensive defender in history behind Virgil Van Dijk, who cost Liverpool £75 million from Southampton earlier this month.
Bilbao said in a statement that Laporte had "completed the requirements for the valid unilateral resolution of his work contract".
It means he is now free to sign for City.
Laporte thanked Athletic's fans in his Twitter message but said he was taking on "a new challenge in my professional career".
"I don't want this to be a goodbye but rather a see you soon," he said.
"Here, I'm leaving a unique and different club and I'll never forget it."
Born in southwest France, Laporte moved to Bilbao's youth team in 2010 and made his debut in 2012 under firebrand Argentine coach Marcelo Bielsa.
He was once a reported target for Barcelona and City wanted to sign him in the close season but he rejected the move. His release clause was 50 million euros at the time.
His signing will mean Guardiola has spent more than £200 million simply on reinforcing his defence alongside the acquisitions of Benjamin Mendy (£52m), John Stones (£47.5m) and Kyle Walker (£45m).
A France international at all youth levels, Laporte has been frustrated at continually being overlooked by senior team coach Didier Deschamps.
He has even mooted the possibility of representing Spain but will now be hoping a high-profile move to the Premier League leaders will catch Deschamps's attention.