The Algerian winger spent five years with the Club after signing in 2018 from Leicester City.
He won an astonishing 11 major trophies with City and leaves the Club as a Treble winner in what was his final campaign.
Blessed with sublime skills and technique, the former African Footballer of the Year became a big crowd favourite among City fans, scoring many memorable goals along the way including several stunning free-kicks and volleys.
He hit double figures for goals in all five seasons at the Etihad, and his 24 in 2021/22 was a career-high.
He was also voted Etihad Player of the Month on seven occasions.
Last season he bagged 15 from 47 appearances, including a stunning hat-trick in the FA Cup semi-final against Sheffield United at Wembley last April – becoming the first Manchester City player to score a treble at the national stadium.
In total, he won the Premier League title four times in five years with the Blues as well as two FA Cups, three Carabao Cups, two Community Shield successes and, of course, leaves as Champions League winner.
He made 46 appearances in the Champions League for City, with his 16 goals meaning an average better than one goal every three games in the competition.
Now he will take on a new challenge in Saudi Arabia.
“To play for Manchester City has been an honour and privilege,” said Mahrez, who will celebrate his 33rd birthday next February.
“I came to City to win trophies and enjoy my football and I achieved all that and so much more.
“I have had five unforgettable years with this football club, working with unbelievable players, fantastic supporters, and the best manager in the world.
“I’ve made a lifetime of wonderful memories and the manner of our Premier League title wins and the battles we’ve had with Liverpool and, last year, Arsenal, underlined our collective desire and mentality to be the best.
“Manchester City will forever be a huge and happy part of my life.”
Reflecting on Riyad’s time with the Club, Director of Football Txiki Begiristain paid his own tribute to the Algeria star.
“Riyad has been a major factor in our amazing successes over the past five years and his contribution will not be forgotten,” he said.
“He is a wonderful footballer to watch and leaves us with so many great memories.
“There are few wingers that possess his levels of skill and technique in world football, and he will be missed, but everyone will wish him all the best as he begins a new chapter in his career.”
Everyone at Manchester City would like to wish Riyad the best of luck in his future career.