SMS Blücher was the last armored cruiser built by the German Empire. She was designed to match what German intelligence incorrectly believed to be the specifications of the British Invincible-class battlecruisers. Blücher was larger than preceding armored cruisers and carried more heavy guns, but was unable to match the size and armament of the battlecruisers which replaced armored cruisers in the British Royal Navy and German Imperial Navy. The ship was named after the Prussian Field Marshal Gebhard von Blücher, the commander of Prussian forces at the Battle of Waterloo in 1815.

The armored cruiser was a type of warship of the late 19th and early 20th centuries. It was designed like other types of cruisers to operate as a long-range, independent warship, capable of defeating any ship apart from a battleship and fast enough to outrun any battleship it encountered.