The Former Barcelona striker will join the Toffees, after Koeman's side met the 21-year-old's buy-out clause of 5.25 million pounds.
The striker joined Barca at the age of 14, before leaving for Malaga last season where he has gone on to score 14 goals in 30 La Liga appearances.
Atletico Madrid had also shown interest in signing Ramirez, but the striker will join Pickford, Klaassen and Onyekuru as another signing at Goodison Park.