The North Ronaldsay or Orkney is a breed of sheep from North Ronaldsay, the northernmost island of Orkney, off the north coast of Scotland. It belongs to the Northern European short-tailed sheep group of breeds, and has evolved without much cross-breeding with modern breeds. It is a smaller sheep than most, with the rams horned and ewes mostly hornless. It was formerly kept primarily for wool, but now the two largest flocks are feral, one on North Ronaldsay and another on the Orkney island of Auskerry. The semi-feral flock on North Ronaldsay is the original flock that evolved to subsist almost entirely on seaweed.
 
The wool from North Ronaldsay sheep is known for its exceptional insulation properties, making it ideal for warm and durable garments.