Galatasaray will pay West Ham a transfer fee of 4.25 million euros ($5 million) while the player will receive an annual wage of 3.85 million euros plus bonuses, the club said in an announcement to the stock market.
Feghouli, 27, who arrived in Istanbul late on Sunday, is expected to be formally introduced to fans on Tuesday.
Galatasaray are seeking to regroup after finishing fourth in the domestic Super Lig last season, well behind champions and Istanbul rivals Besiktas.
For the new season, the club have already signed French international striker Bafetimbi Gomis, Moroccan international midfielder Younes Belhanda and Brazilian midfielder Fernando.
But Croatian coach Igor Tudor still has to convince fans he is the man for the job.
Galatasaray’s season started in the worst possible way with the side knocked out by Swedish outfit Ostersund in the the Europa League second qualifying round.
