SMS Cormoran or SMS Cormoran II was a German armed merchant raider that was originally a German-built Russian merchant vessel named Ryazan. The ship was active in the Pacific Ocean during World War I. Built in 1909, she was captured by the German light cruiser on 4 August 1914 and converted into a raider at the German colony Kiautschou. She was forced to seek port at Apra Harbor on the U.S. territory of Guam on 10 December 1914. The United States, then declared neutral in the war, refused to supply provisions sufficient for Cormoran to make a German port. After the U.S. declaration of war on April 6, 1917, the Naval Governor of Guam informed Cormoran that she would be seized as a hostile combatant, prompting her crew to scuttle her.
Ryazan was built at the Schichau shipyard in Elbing, Imperial Germany in 1909 for the Russian merchant fleet (Rjasan or Rjäsan, from the Russian town of Ryazan). She was used by imperial Russia as a combination passenger, cargo and mail carrier on North Pacific routes.
The Ryazan was captured southeast of the Korean peninsula by the German light cruiser on 4 August 1914 as the first prize of World War I from the Russian empire. She was taken to Qingdao in the German colony Kiautschou, where she was converted to an armed merchant raider. The new Cormoran replaced the original SMS Cormoran, a small shallow draft cruiser that had a long Imperial Navy career in the Pacific, having taken part in the events that brought Kiautschou into the German colonial empire in 1897–98. The old Cormoran was laid up at Qingdao with serious maintenance issues and unable to go to sea, and her armaments were transferred to the captured merchant ship.
On 10 August 1914, the new Cormoran (or Cormoran II) left Qingdao harbor and sailed through the South Pacific region. After Japan declared war on the German Empire, her warships discovered and pursued the Cormoran, forcing her to seek refuge in Apra Harbor, in the U.S. Territory of Guam, on 14 December.