Roma had been leading the match 3-0 after 51 minutes, but conceded four goals to slump to their fourth consecutive defeat and prompt the former Chelsea boss’s exit.
“I’ve always thought about the good of Roma and after a game such as today’s I believe it’s right to give a signal,” he said. “After the final whistle I went into the changing rooms to thank the team and I decided to hand in my resignation.”
Cash-strapped Roma, who are in the process of being sold, lost 3-2 at home to Ukrainians Shakhtar Donetsk in the Champions league last-16 first leg on Wednesday.
Around 200 fans protested at Roma’s training ground on Saturday, throwing flares and firecrackers at the gates before being dispersed by police.
After leading Roma to a second place finish in Serie A lasy season, Roma have struggled since the winter break and are in eighth position in the league and have not won their last five games in all competitions.
Retired former Roma striker Vincenzo Montella could take over in a caretaker role but it is unclear who would make the decision given the club’s circumstances.
Rosella Sensi remains the president until the club is bought but creditor bank UniCredit has been in de facto control for months as it looks to recoup debts from a sale which has dragged on and stopped Ranieri buying players in January.
However, the club hierarchy were already pondering Ranieri’s position before he resigned.
“We want to think about things calmy. We will make a decision with our head,” director Gian Paolo Montali said straight after the Genoa game.