The 29-year-old is believed to have cost the Toffees an initial £8.5m and could raise to more than £10m with bonuses.
The former Aston Villa man has already joined up with the Everton squad in Switzerland ahead of their third pre-season friendly of the summer against Monaco on Wednesday.
He becomes Everton’s third summer signing following goalkeeper Jonas Lossl and midfielder Andre Gomes.
✅ High Quality— Everton (@Everton) July 15, 2019
Welcome, Fabian Delph! pic.twitter.com/qFHSccvUpF
Delph was surplus to requirements at Etihad Stadium after the £60m signing of midfielder Rodri from Atletico Madrid and left-back Angelino from PSV.
He was about to enter the final 12 months of his contract with the Premier League champions so was available for a knockdown fee.
Speaking about his move to Goodison Park, Delph said:
“I’m hungry. I don’t like losing. I see myself as a winner.
“The club that I’ve been at has had success, especially in the last two seasons, and over the last four years we managed to win trophies. I wanted to be playing more regularly and the opportunity to come and play for Everton Football Club was too good of an opportunity to turn down.
“I’m at an age now where I am probably one of the most experienced players, so hopefully I can bring that and try to help my teammates here to do better. Ultimately, the goal is to win something.
“I’ve not come here just to be here - I’ve come here with ambitions to win things.”
The deal has split Evertonians on social media, with some questioning the wisdom of signing a 29-year-old midfielder when we are looking to shed the squad of ageing players.
Others will point to the fact that Delph is an England international, versatile and experienced, while his relatively low transfer fee minimises the risk.
I think the deal will only be put in proper perspective once the window has closed and we can assess what Delph’s role will be in the squad.
Marcel Brands has stated that he is looking to invest heavily in young players this summer but would look to bring in older players if the price was right.
It seems Delph fits in with that profile, and a three-year deal makes a lot of sense considering he's already 29, though he's not gotten a lot of mileage in the last four seasons.