HMS Cardiff was a C-class light cruiser of the Royal Navy, named after the Welsh capital city of Cardiff. She was part of the Ceres group of the C-class of cruisers.
The steps to Cardiff occurred in quick procession, from being ordered under an Emergency Plan in April 1916 due to World War I, then to being laid down in July 1916 by Fairfield Shipbuilding & Engineering Company, to the culmination of her being launched in April 1917. She was part of a light cruiser class of five ships known as the Ceres-class.
She was commissioned in 1917, becoming flagship of the 6th Light Cruiser Squadron, part of the Grand Fleet in July 1917. In 1918, the war had come to a close, and Cardiff had the honour of leading the German High Seas Fleet to the River Forth. The German ships were to be interned under the terms of the armistice, but remained under German command. The German Fleet was later scuttled under the orders of its commanding officer, Admiral Ludwig von Reuter to ensure they did not fall into the hands of the victors. In November 1921 she escorted the Austro-Hungarian Imperial-Royal couple to Madeira. Though World War I was over, her service was not. She deployed to the Baltic Sea, operating near Reval (Tallinn), Estonia against the Bolsheviks in operations that also involved Allied ground troops.
Between the wars Cardiff, now obsolescent, served overseas; in the early 1930s, she was the flagship of the Navy's Africa Station.
Cardiff survived to see yet another war, though she would not see action. After a brief period escorting convoys, in which she was involved in the pursuit of the German battleships Scharnhorst and Gneisenau after the sinking of HMS Rawalpindi. She was then converted for use as a training ship. She was sold on 23 January 1946, and broken up at the yards of Arnott Young, Dalmuir, Scotland from 18 March 1946.