Kronprinzessin Cecilie was a Hamburg America Line (HAPAG) ocean liner.

The United Kingdom captured her in 1914, and converted her in 1915 into a dummy of the battleship HMS Ajax, as which she operated from northwest Scotland.

In 1916 she was converted into HMS Princess, a real Royal Navy armed merchant cruiser, as which she took part in the East African campaign.

The ship is sometimes confused with the Norddeutscher Lloyd transatlantic liner Kronprinzessin Cecilie,[1] which was launched only a year later.

The ship was the second of a pair of sisters that HAPAG commissioned, one from the Fairfield Shipbuilding and Engineering Company in Glasgow, and the other from Friedrich Krupp Germaniawerft in Kiel.

[3] Kronprinzessin Cecilie had one single-ended and three double-ended boilers, with a working pressure of 214 pounds per square inch (1,480 kPa).

[5] On 14 March 1906 she left Hamburg on her maiden voyage, which was to Tampico and Vera Cruz in Mexico.

[3] On 2 February 1907 she left HAPAG's terminal at Hoboken, New Jersey with passengers for the West Indies.

[3] In April 1914 the USA caught the HAPAG ship Ypiranga gun-running for President Victoriano Huerta's army in the Mexican Revolution.

On 8 May it was alleged that Kronprinzessin Cecilie had arrived in Puerto Mexico (now Coatzacoalcos) carrying arms.

[15][16] On 10 May Admiral Badger, who was in Vera Cruz, reported that although Kronprinzessin Cecilie was carrying arms and ammunition, they were not unloaded in Puerto Mexico, and she would take them back to Hamburg.

On 10 May Emilio Rabasa, Agustín Rodríguez, and Luis Elguero embarked on Kronprinzessin Cecilie at Vera Cruz to travel as far as Havana,[19] where they were to change ships to reach Key West, Florida.

Kronprinzessin Cecilie was delayed in Vera Cruz, waiting to embark refugees who were expected from Tampico.

[21] The ship reached Havana on 14 May, where Rabasa, Rodríguez, and Elguero made their connection to Key West.

A French Navy cruiser pursued Kronprinzessin Cecilie, which took refuge in Falmouth, Cornwall.

[3][24] On 21 October 1914 the Admiralty ordered the conversion of Kronprinzessin Cecilie into a dummy of the battleship HMS Ajax.

On 13 September she and other Royal Navy ships landed troops at Mikindani, near the border with Moçambique.

[25] Apart from a visit to Palma on 8–10 December 1916, just over the border in Moçambique, Princess continued to patrol the coast of German East Africa.