Nidaros, Niðarós or Niðaróss was the medieval name of Trondheim in Norway, when it was the capital of the country's first Christian kings. It was named for its position at the mouth (Old Norse: óss) of the River Nid (today's Nidelva).

Nidaros, Niðarós or Niðaróss was the medieval name of Trondheim in Norway, when it was the capital of the country's first Christian kings. It was named for its position at the mouth (Old Norse: óss) of the River Nid (today's Nidelva).