North Ronaldsay lies around north of its nearest neighbour, Sanday, at . It is around long and is defined by two large sandy bays; Linklet Bay on the eastern shoreline and South Bay at the south. The west of the island is very rocky, with many skerries. North Ronaldsay is low-lying and exposed; its climate is extremely changeable and frequently inclement. The surrounding waters are stormy and treacherous, and have been a notorious "graveyard" for ships (hence the unusually early provision of a lighthouse on the island).
