The church of St Mary and St Martin in Blyth was severely vandalised, with a stained glass window smashed, an effigy of a knight damaged, a knife plunged into the bell tower door and religious objects desecrated.
The 13th century effigy of a knight was damaged after bricks were thrown at it. Other artefacts were damaged, graffiti scrawled on the walls, cash stolen and several pieces of religious literature damaged.
The church is one of the oldest examples of Norman architecture in the country, dating back to 1088.
Police are treating the incident as a heritage crime and are appealing for witnesses. "This was an appalling attack on a beautiful and historic building," said Inspector Rob Harrison, highlighting the community's distress and appealing for the public's help.