The first HMAS Sydney was a Chatham class light cruiser of the Royal Australian Navy. She was laid down by the London and Glasgow Engineering Company at Govan, Scotland, in February 1911, launched on 29 August 1912 by Lady Henderson, wife of Admiral Sir Reginald Henderson and commissioned on 26 June 1913 at Portsmouth, England.

Sydney made history during World War I on 9 November 1914, near the Cocos Islands in the Indian Ocean. Detached from convoy escort duty to investigate the reported "strange warship approaching" from the Cocos Islands WT Station, Sydney came into action with the German light cruiser SMS Emden. The action lasted over an hour and resulted in Emden being wrecked and aground on North Keeling Island reef.

During the remainder of World War I Sydney served in British waters. In 1918 she operated a Sopwith Pup plane, launched from a platform fitted over a gun mounting. After the war Sydney continued to serve on the Australian station, including a period spent as flagship.

Sydney paid off at Sydney on 8 May 1928 and arrived at Cockatoo Island, Sydney, on 10 January 1929 where she was broken up.

See HMAS Sydney for other ships of this name.