SMS Undine[a] was the last member of the ten-ship Gazelle class of light cruisers that were built for the German Kaiserliche Marine (Imperial Navy) in the late 1890s and early 1900s.

Built to be able to serve with the main German fleet and as a colonial cruiser, she was armed with a battery of ten 10.5 cm (4.1 in) guns and had a top speed of 21.5 knots (39.8 km/h; 24.7 mph).

Undine was a modified version of the basic Gazelle design, with improved armor and additional coal storage for a longer cruising range.

She also took part in training maneuvers with other elements of the fleet, and during one of these exercises in November 1905, she accidentally rammed and sank the torpedo boat SMS S126.

After the outbreak of World War I in August 1914, Undine was deployed to the Baltic Sea, serving in the Coastal Defense Division.

Undine carried 700 t (690 long tons) of coal, which gave her a range of 4,400 nautical miles (8,100 km; 5,100 mi) at 12 knots (22 km/h; 14 mph).

She was launched on 11 December 1902, and during the ceremony, Prince Otto zu Salm-Horstmar, the president of the Flottenverein (Navy League), gave a speech.

After her launching, fitting-out work commenced, and she was commissioned to begin sea trials on 5 January 1904 under the command of Korvettenkapitän (KK—Corvette Captain) Carl Schaumann.

Throughout the year, she took part in the normal peacetime routine of training exercises, which included shooting practice in the waters off Helgoland from 8 to 12 October.

[9][10] From 3 May to 9 June 1906, the ship underwent repairs to her bow as a result of the damage incurred in the collision with S126; the work was performed at the Kaiserliche Werft (Imperial Shipyard) in Wilhelmshaven.

By late in the year, Undine was becoming worn out, which necessitated a major overhaul at the Kaiserliche Werft in Danzig that lasted from 26 September to 17 October.

Undine was assigned to the Training Squadron in April before being decommissioned in Danzig on 12 July for another major overhaul; during this last stint in service, her commander was Fregattenkapitän (Frigate Captain) Andreas Fischer.

[11] After the outbreak of World War I in July 1914, Undine was recommissioned on 4 August and assigned to the Coastal Defense Division in the western Baltic.

She initially patrolled the line between Dornbusch and Møn, and was briefly assigned to the Detached Division under KAdm Ehler Behring.

She took part in a sortie into the Gulf of Finland that occurred from 3 to 9 September under the direction of Prince Heinrich of Prussia, the supreme commander of naval forces in the Baltic.

Over the following months, she served intermittently as the flagship of Vizeadmiral (Vice Admiral) Robert Mischke, the commander of the Coastal Defense Division.

[12][13] On 7 November 1915, Undine was steaming north of Arkona with a pair of torpedo boats as escort for the ferry Preussen as it moved from Trelleborg to Sassnitz.

Casualties were relatively minor, but the number is unclear: according to Erich Gröner, fourteen men were killed, but Hans Hildebrand, Albert Röhr, and Hans-Otto Steinmetz report that twenty-five died.