The 21-year-old enjoyed his most productive campaign in front of goal last term in Ligue 1, scoring six goals and providing two assists as Bruno Genesio's men finished fourth in the French top flight.
Doku burst onto the scene at Belgian outfit Anderlecht before sealing a switch to Rennes in October 2020, and he has since cemented himself as a regular for the Red and Blacks.
The attacker also possesses respectable international pedigree, having featured for Belgium on 14 occasions since making his debut for the Red Devils in August 2020.
According to Sky Sports News, Manchester City have agreed a transfer fee with Rennes for the signing of Doku, with the winger looking set for a move to the Premier League.
The report claims that the Citizens will pay £55.5m for the services of the attacker, who is preparing to become Man City's third arrival of the summer window.
Mateo Kovacic joined from Premier League rivals Chelsea to bolster Pep Guardiola's engine room, while Josko Gvardiol was recruited from RB Leipzig to give the English champions greater options in defence.
The treble winners have seen a lot of first-team players leave the Etihad this summer, with Man City hoping to bring Doku to the club as a replacement for Riyad Mahrez.
The Algerian ended his five-year stay in Manchester to sign for Saudi Pro League outfit Al Ahli, joining the likes of Edouard Mendy and Allan Saint-Maximin at the Jeddah-based club.
Despite the recent performances of youngster Cole Palmer, it is understood that the Premier League champions are looking to improve their winger options before the window slams shut on September 1.
England Under-21 international Palmer made the net ripple during both the Community Shield meeting with Arsenal and the UEFA Super Cup final against Sevilla, however the attacker has been restricted to just 10 minutes of Premier League action so far this term.
It was reported last week that Chelsea were set to join Man City in the race for Doku after failing to sign Crystal Palace playmaker Michael Olise.
The Blues are said to have activated the £35m release clause in Olise's deal at Selhurst Park, however the France youth international later went on to sign a fresh four-year contract with the Eagles.
Depending on how fast a deal for Doku can be finalised, Man City could be in the position to hand the 21-year-old his debut when they travel to Sheffield United on Sunday afternoon.