Man City Coach, Guardiola
Manchester City have been banned from European club competition for the next two seasons after being found to have committed "serious breaches" of Uefa's club licensing and financial fair play regulations.
The reigning Premier League champions have also been fined 30m euros (£25m).
The decision is subject to appeal to the Court of Arbitration for Sport.
Manchester City say they are "disappointed but not surprised" by the "prejudicial" decision and will appeal.
The independent Adjudicatory Chamber of the Club Financial Control Body (CFCB) said City had broken the rules by "overstating its sponsorship revenue in its accounts and in the break-even information submitted to Uefa between 2012 and 2016", adding that the club "failed to cooperate in the investigation".
It has been reported that City could also face a Premier League points deduction because the league's FFP rules are similar - although not exactly the same - as Uefa's.
However, the punishment has no implications for City's women's team.
Manchester City said in a statement: "The club has always anticipated the ultimate need to seek out an independent body and process to impartially consider the comprehensive body of irrefutable evidence in support of its position.
"In December 2018, the Uefa chief investigator publicly previewed the outcome and sanction he intended to be delivered to Manchester City, before any investigation had even begun.
"The subsequent flawed and consistently leaked Uefa process he oversaw has meant that there was little doubt in the result that he would deliver. The club has formally complained to the Uefa disciplinary body, a complaint which was validated by a CAS ruling.
"Simply put, this is a case initiated by Uefa, prosecuted by Uefa and judged by Uefa. With this prejudicial process now over, the club will pursue an impartial judgment as quickly as possible and will therefore, in the first instance, commence proceedings with the Court of Arbitration for Sport at the earliest opportunity."
City have been drawn to face Real Madrid in the last 16 of this season's Champions League, with the first leg to be played on 26 February at the Bernabeu.
La Liga President Javier Tebas praised Uefa for "finally taking decisive action".
"Enforcing the rules of financial fair play and punishing financial doping is essential for the future of football," he said.
"For years we have been calling for severe action against Manchester City and Paris Saint-Germain, we finally have a good example of action and hope to see more. Better late than never."