In a statement Udinese said that Cannavaro "has signed a contract until June 30, 2024", the 2006 World Cup winner also bringing in his brother Paolo on his coaching staff.
Cioffi was dismissed after Udinese fell to a 1-0 defeat at fellow strugglers Verona on Saturday, a loss which left them locked on 28 points with Frosinone who are just inside the relegation zone.
Former Ballon d'Or winner Cannavaro, 50, will be in charge on Thursday when Udinese play the final 18 minutes of their home clash with Roma.
Play in that match just over a week ago was suspended with the teams level at 1-1 after Roma defender Evan Ndicka collapsed on the pitch with what was initially feared to be a heart problem.
However tests later revealed that the Ivory Coast international had suffered "a thoracic trauma with minimal left pneumothorax (trapped air between the lung and chest wall)".
Cannavaro has had a mixed coaching career, working in the Gulf and China --- where he won the Super League in 2019 -- before a short-lived spell at lower league outfit Benevento last season.
Udinese have a tough run-in after finishing the Roma match, with matches against Bologna, Napoli and in-form Lecce before relegation six-pointers against Empoli and Frosinone in the final days of the campaign.
