SMS "Mainz" was a light cruiser of the German "Kaiserliche Marine" (Imperial Navy) during the First World War. She had three sister ships, , , and . She was built by the AG Vulcan shipyard in Stettin; her hull was laid down in 1908 and she was launched in January 1909. She was commissioned into the High Seas Fleet in October 1909. She was armed with a main battery of twelve 10.5 cm SK L/45 guns and had a top speed of .