Thomas Partey becomes the seventh signing for Arsenal this summer, with the club having already signed Willian on a free transfer from Chelsea and defender Gabriel from Lille for £27m.
The London side also agreed permanent deals for Cedric Soares and Pablo Mari, who had been on loan at the club, and extended the loan deal for Dani Ceballos from Spanish giant, Real Madrid for a second year.
Goalkeeper Alex Runarsson become the Arsenal’s sixth signing, joining from Ligue 1 club Dijon on a four-year deal.
Arsenal boss Mikel Arteta talks about Partey after the 27-year-old signed a £220,000-a-week contract on a four-year deal, with an option for another season.
Mikel Arteta said: “We have been watching Thomas for a while, so we’re now delighted to add such a high quality player to our squad.
“He is a dynamic midfielder with great energy. He brings a lot of experience from a top club that has competed at the highest level in La Liga and the Champions League for several years.
“We’re very impressed with his attitude and his approach to the game. He’s an intelligent footballer, and we’re looking forward to him integrating into our system and contributing to the progress we’re building at the moment at the club.”
The Ghanaian international will wear jersey number 18 following his £45m switch from Atlético Madrid.