The Guarnak-Sylmahn Canal was a major canal in the Republic of Siddarmark, flowing down through the center of the Sylmahn Gap.

It connected the uppermost navigable reaches of the Sylmahn River to the Hildermoss River, six hundred and fifty miles to the northwest, and via the Guarnak–Ice Ash Canal, to the Ice Ash River five hundred and thirty miles to the northeast. To the south, the Canal connected to the Tairmana and Siddar canals, giving direct access to the capital, seven hundred and twenty miles to the southeast. (map)

The Canal had many locks, including the Serabor Locks, near the city of Serabor. (MTAT)