Grim Brigs (Grid reference NO9091) is a rocky headland on the North Sea at Muchalls, Scotland.[1] Notable historic features in this vicinity include St. Ternan's Church, Muchalls Castle and Elsick House. Approximately one kilometre inland is the noted medieval drovers' road known as the Causey Mounth. The geology of Grim Brigs is associated with the harder rock formations north of the Highland Boundary Fault, which forms the boundary between the Scottish Highlands and Lowlands. This Highland Boundary Fault emerges at the North Sea approximately four kilometres south of Grim Brigs near the Chapel of St. Mary and St. Nathalan.