Pope Francis is to replace the controversial Cardinal Secretary of State, Tarcisio Bertone in a signal that management of Vatican affairs is to change course.
Bertone, 79, is to announce his resignation imminently, Vatican sources told La Stampa.
Archbishop Pietro Parolin, the Holy See emissary to Venezuela, will be appointed new secretary of state, the second-highest Vatican post, which is often referred to as vice-pope.
Parolin, 58, an Italian native form the Vicenza province, will effectively take office in October.
Appointed by Benedict XVI in 2006, Bertone's seven-year rule has been marred in controversy and his replacement was widely expected.
The 79-year-old owes much of his reputation to his role as head of the commission of cardinals supervising the scandal-dogged Vatican bank, officially known as the Institute for Religious Works (IOR), but he will temporarily keep that job.
Bertone has been accused of being the fiercest opponent of papal attempts to reform and clear up the bank.
Earlier in August, Francesca Chaouqui, the only female member of a new papal committee tasked with overhauling the Vatican's murky financial administration, caused embarrassment to the Holy See by tweeting that Bertone was corrupt.
Chaouqui's committee was set up by Francis, after a senior cleric who was arrested by Italian police accused a group of cardinals, including Bertone, of covering up illicit dealings.
Monsignor Nunzio Scarano, 61, a former Vatican finance official, was detained in June for allegedly trying to smuggle €20m (£17m) into Italy from Switzerland.
Scarano wrote to Francis claiming to have witnessed numerous abuses during his long career at the Vatican office managing all the Holy See's properties, a business linked to the IOR.
Scarano claimed that three senior cardinals, including Bertone, knew about the abuses but failed to act and turned a blind eye instead.
According to Corriere Della Sera newspaper, it was this scandal that cost Bersone his job.