Relegated Bournemouth have accepted a £40m bid from Manchester City for defender Nathan Ake.
It is understood there is an additional £1m in add-ons as part of the deal.
Netherlands international Ake, 25, joined Bournemouth in 2017 for a club record fee and has made 121 appearances for the Cherries.
Manchester City manager Pep Guardiola has been targeting at least one centre-back to bolster his squad next season and Ake has been a target for a while.
Bournemouth were relegated from the Premier League after finishing 18th, while Manchester City finished runners-up.
It was understood Ake would leave Bournemouth this summer whether Eddie Howe's men stayed in the top flight or not. However, their relegation was the trigger for City to open talks.
Ake, who played 29 of Bournemouth's 38 games in the Premier League this season, has been capped 13 times by his country and has previously played club football for Chelsea, Watford and Reading.
Last year, Bournemouth sold defender Tyrone Mings to Aston Villa for £20m which is currently the highest fee received for a player by the Cherries.
'Ake fits Guardiola template superbly' - Analysis
BBC Sport's Simon Stone
Following Sunday's final Premier League game against Norwich, Manchester City sporting director Txiki Begiristain said the club intended to "move fast" to strengthen their squad this summer.
I don't think anyone appreciated quite how fast.
On Wednesday, City advanced talks with Valencia winger Ferran Torres, which will see the Spain Under-21 international become the club's replacement for Leroy Sane for around £20m. Now, the Ake deal is almost done.
One of the obvious reasons why City lost the Premier League title to Liverpool was their failure to sign a replacement for Vincent Kompany.
It is significant that after the 3-2 defeat by Norwich on 14 September, Guardiola's two most experienced central defenders, Nicolas Otamendi and John Stones, did not start another Premier League game together until July.
Both stayed on the bench throughout the rematch with Norwich, when 19-year-old Eric Garcia started, before being replaced by Fernandinho at half-time.
It is a prerequisite for Guardiola that his defenders are able to take passes in tight situations and trigger attacks. Ake fits this template superbly.
He is also good in the air, which is one of 35-year-old Fernandinho's weaknesses after he was pressed into service in the makeshift role as Stones or Otamendi - and sometimes both - were ignored.
It might not be the end of the spending either, with more defensive reinforcements anticipated.
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