SS Arcadian was an ocean liner launched in Barrow-in-Furness in 1899 by Vickers, Sons & Maxim Ltd for the Pacific Steam Navigation Company as Ortona.

[1] On the first leg of this voyage Olave St Claire Soames met Lieutenant General Sir Robert Baden-Powell, the founder of the Scout Movement, leading to their marriage in October of that year.

[5] On 7 April 1915 at Alexandria, General Sir Ian Hamilton came aboard and used Arcadian, together with the battleship HMS Queen Elizabeth, as his headquarters ship during the opening phase of the Gallipoli Campaign.

[5] On 15 April 1917 Arcadian was en route from Salonika (now Thessaloniki) to Alexandria with a company of 1,335 troops and crew and escorted by an Imperial Japanese Navy destroyer.

Shortly after completing a boat drill, while 26 miles north east of the Greek island of Milos, Arcadian was hit by a single torpedo from the German submarine SM UC-74 and sank within six minutes with the loss of 279 lives.