Rakan Said al-Juburi told AFP it was the 14th such discovery in the area.
"Local residents and shepherds guided security forces to the mass grave which appears to contain the remains of more than 75 civilians and security personnel," he said.
The governor said the victims had been "savagely executed by jihadists who occupied Hawija", one of the last urban centres held by the Islamic State (IS) group before its ouster last year by Iraqi security forces.
Residents fear that many missing relatives and friends, especially members of the security forces, have probably suffered the same fate.
Security forces have discovered dozens of mass graves since they drove out IS in 2017 after three years of occupation of swathes of northern and western Iraq.