West Ham United have signed Greece defender Konstantinos Mavropanos from Stuttgart for an undisclosed fee.
Mavropanos, 25, has signed a five-year contract with the Hammers and has taken the number 15 shirt.
Arsenal signed him in January 2018 but only made seven Premier League appearances before being loaned out.
"I'm looking forward to the next step in my career," he said. "I will give everything for the shirt.
"I am really happy and excited to be here and back in the Premier League."
Mavropanos, who has been capped 19 times by Greece, becomes West Ham's third summer signing after midfielders James Ward-Prowse and Edson Alvarez arrived from Southampton and Ajax, respectively.
He played 34 times for Stuttgart in all competitions last season as the German side narrowly avoided relegation and made 89 appearances overall, scoring eight goals.
Mavropanos joined the Bundesliga club from Arsenal on a season-long loan in July 2020, which was extended for a second season before the move was made permanent.
Hammers boss David Moyes backed Mavropanos to provide competition to the club's existing defenders.
"I'm pleased to welcome Konstantinos to West Ham," said the 60-year-old Scot.
"We've been looking to add to our centre-half options this summer, so it's good we've brought in an international defender of his ability.
"We're looking forward to integrating him into the group.”
