Libero Milone, who had the job of ensuring there was transparency in the finances at the headquarters of the Roman Catholic Church, had been expected to serve in his position until 2021.
A statement released by the Vatican gave no reason for the resignation of the 68 year old Italian, who is a former chairman and CEO of the global auditing firm Deloitte in Italy. Instead, it stated Milone's relationship with the Vatican had been concluded "by mutual accord".
Following Milone's appointment in 2016, Cardinal George Pell who is head of the Vatican's Secretariat for the Economy, said he would be answerable only to the pope and free to "go anywhere and everywhere" in the Vatican in order to do his job.
Pope Francis, who reportedly personally accepted Milone's resignation, has introduced a series of reforms in a bid to reform Holy See finances and make them more transparent after a number of scandals since he was elected in 2013.
Milone, a former employee of Deloitte, Fiat and Wind Telecom came under the spotlight last June when an external audit by accountancy firm PricewaterhouseCoopers (PwC) was abruptly ended after just four months and the probe was given instead to the general auditing office.
The Vatican said a search for Milone's replacement would begin "as soon as possible".
