With the transfer of Mendy, Manchester City spent over 200 million pounds in this transfer window.
The Ligue 1 victor joins the Mancunian giants on a five-year contract, for a reported fee of £52m.
It's questionable as to whether Pep Guardiola needed him anyway, as with an abundance of options in midfield and in attack, Nasri would unlikely have a role to play for City if he stayed.
Guardiola might come under pressure next season at City as the club he joined past year has now splashed just under than £300 million (R5 billion) on defensive players since 2014. For such a young player, he has a wealth of top-level experience.
Mendy has signed a five-year deal with the cash-rich club and will join his new squad in the United States of America as they get ready for their second pre-season game against Real Madrid in LA.
"Football is very dynamic and it requires quality players in every position, so I think a player who can play in different positions at a good level has an advantage, and becomes very important for the team as well", he said.
"Monaco were one of the most attractive teams in Europe last season".
Several clubs have been strongly linked with him including Premier League rivals Manchester City and French giants Paris Saint-Germain.
He played in the final seven Premier League games of the season, of which City won five, drew two, conceded just four times and, crucially, secured a third-place finish and automatic qualification for the Champions League group stage.
With sky-blue trim on the shirt and socks, the latest in a long line of maroon kits offers a nod to City's league title-winning side of 1967/68.
After a spectacular campaign with the Principality outfit, and eventual Ligue 1 champions, the France global has moved on to pastures new.
His arrival follows those of Bernardo Silva, Ederson, Kyle Walker and Danilo and City may not be finished there with reports continuing to link the club with further additions, most notably Arsenal's Alexis Sanchez.