Chelsea suffered a 3-0 defeat at Juventus on Tuesday, a match that proved to be Di Matteo's last at the helm of the reigning European champions.
Benitez, who has been out of work for two years since being axed by Inter Milan after only six months at the San Siro, takes the Stamford Bridge reins on a deal until the end of the season. It is the second successive time he has taken charge of Champions League holders.
Before his spell at Inter, the Spanish boss spent six years in charge of Liverpool, where he had the upper hand on Chelsea in a number of high-profile encounters - including Champions League semi-finals in 2005 and 2007.
Coincidentally he will take Chelsea to the Club World Cup in December - a competition that he won as Inter boss before being sacked just days after lifting the trophy.
A statement on Chelsea's official website said: Chelsea Football Club can confirm Rafael Benitez has been appointed interim first-team manager until the end of the season.
"The owner and the board believe that in Benitez we have a manager with significant experience at the highest level of football, who can come in and immediately help deliver our objectives.
"The 52-year-old Spaniard is due to meet the players at the training ground in Cobham tomorrow."
In March, ESPN broke the story that Benitez was first under consideration for the Chelsea job before Andre Villa-Boas was sacked, with talks breaking down because the Spaniard wanted an 18-month contract and the deal on offer was only until the end of the season.
But with a similarly short-term deal on the table this time around, Benitez changed his mind and is prepared to try to prove himself between now and next May, with a clause thought to be included that would see him granted a full season in 2013-14 should he turn results around.
Benitez is in Abu Dhabi for a scheduled appearance at a coaching conference, but is now making plans to fly into Manchester on Thursday morning.
He told Sport360° on Wednesday: "I have just found out [about Di Matteo]. Obviously Chelsea is a top side and they can compete for trophies so it goes in this category."
Asked if Chelsea had already made an approach, he replied: "You ask directly, I cannot answer directly. In football a lot of people are talking so we will see what happens in the next few days. I am looking for a club that can challenge for trophies and Chelsea is one of these clubs."
Despite the impending appointment of Benitez, Blues owner Roman Abramovich is still thought to want to bring former Barcelona coach Pep Guardiola to Stamford Bridge as a long-term managerial option next summer.
Guardiola remains on a year's sabbatical in New York but will start planning his future early in the New Year, indicating that Benitez has an even shorter period to impress.
Abramvoich opted to inform Di Matteo of his dismissal at 4am GMT on Wednesday morning, when he arrived back at the club's Cobham training ground from Turin.
ESPN sources have explained that conversations between Abramovich's close aides, and board members, had taken place immediately after the damaging defeat at Juventus, which could see Chelsea become the first Champions League holders to be eliminated in the group stage.