Conor O'Shea has resigned from his role as Italy head coach with immediate effect, the Italian rugby federation announced on Saturday.
The 49-year-old Irishman's contract had been due to run through to the end of May 2020.
"We have started a process and generated a new, well-founded hope, but I also believe that the end of the Rugby World Cup represents the best time for everyone to make changes in view of the new cycle," said O'Shea.
"I loved every minute I spent in Italy and I really believe in what we have done and how it can be achieved in the years to come."
The former London Irish and Harlequins director of rugby has been linked with a role in the English RFU as this year's World Cup finalists build towards the 2023 tournament in France.
"We are saddened by Conor's decision not to complete the journey as contractually intended," said Italian Rugby Federation president Alfredo Gavazzi.
"We thank him for the commitment and passion which he has shown in his role over these years and we wish him the best professional successes."
Italy failed to progress past the pool stage in the World Cup in Japan.
They beat Namibia (47-22) and Canada (48-7) but their match against New Zealand was called off because of a typhoon and they suffered a heavy 49-3 defeat to eventual champions South Africa.
Nevertheless, the 35-times capped former Ireland fullback had been expected to remain at the helm until after the 2020 Six Nations.
O'Shea, who led Harlequins to the Premiership title in 2012, replaced Jacques Brunel on the Italy bench on a four-year contract back in March 2016.
But despite his successes with London Irish and Harlequins he failed to turn around the fortunes of Italian rugby, and never won a match in the Six Nations.
The last Italian victory in the tournament was against Scotland in Edinburgh in February 2015, while at home the Azzurri have not won since March 2013, when they beat Ireland in Rome.
The highlight of O'Shea's reign was a historic 20-18 success against South Africa in Florence in November 2016.
The defeat was a low point for the Springboks who rebounded to win their third World Cup trophy.
"I sincerely hope to have left Italian rugby in a better position," continued O'Shea.
"I built friendships and made experiences that I will never forget.
"The young people who are coming through join a system that, by continuing with the right decisions, can only improve in the years to come."
Former Scotland coach Vern Cotter is among the names being touted to replace O'Shea, along with fellow New Zealander Dave Rennie, currently in charge of Glasgow Warriors.
Cotter, 57, was hired as Montpellier's head coach in 2017, but moved to the director of rugby role earlier this year.
Former Wales assistant coach Rob Howley had been seen as a potential candidate before being sent home from the World Cup for allegedly breaching betting rules.
Former Cheetahs coach Franco Smith is also set to join Italy as their director of rugby, but it's not sure whether he'll also be entrusted with the head coaching responsibilities.