The Stonewall Formation is a stratigraphical unit of Late Ordovician to Early Silurian age in the Western Canadian Sedimentary Basin.

Two thin sandstone beds occur in the middle and at the top of the formation.

[1] In the central Williston basin, the base is marked by an anhydrite bed.

The Stonewall Formation occurs at surface in the Manitoba outcrop belt and in the sub-surface in the Williston Basin.

The Stonewall Formation is overlain by the Interlake Group (conformably in the south, disconformably in the north) and sharply overlays the Stony Mountain Formation.