The Turkish club announced his arrival on Monday night after he rejected an offer to stay at Crystal Palace, as well as contracts at Lazio, Al-Nassr and Gala’s rivals, Fenerbahce.
As part of Zaha’s unveiling, it was confirmed that he will recieve a €2.3million (£2m) signing-on fee for joining the Istanbul team.
He will also earn a €4.35m (£3.75m) net annual wage which breaks down to around £72,000-a-week.
Galatasaray won over Zaha despite Palace’s contract being thought to be in the £200,000-a-week region.
The Ivory Coast international will hope to reach the Champions League group stage with his new club, who have been drawn to face Lithuanian side Zalgiris in the second round of qualification this month.
Zaha bid an emotional farewell to Palace before his move was confirmed.
He posted on Instagram: “As I start a new chapter, I want to speak to you Palace fans who mean so much to me.
“We have been through so much together, including 10 years in the Prem. There are loads of amazing memories. I’m so proud to have played my part in getting us to the Prem and helping to keep us there.
“I’ve been wearing the Palace shirt since I was 8 years old, it’s literally been my second skin and I always gave EVERYTHING when I wore it.
“I grew up two roads away from the bright lights and loud crowds of Selhurst Park, having no idea that I would be at the centre of it all one day.
“I want to thank Steve Parish, all of my team-mates, coaches and the entire Palace fanbase for always believing in me and encouraging me to get to where I am today. From the bottom of my heart, I’m forever grateful.”