The County class was a class of heavy cruisers built for the Royal Navy and Royal Australian Navy in the years between the First and Second World Wars. They were the first 'post-war' cruisers constructed for the Royal Navy and were designed within the limits of the Washington Naval Treaty of 1922. Such ships, with a limit of 10,000 tons standard displacement and 8-inch calibre main guns may be referred to as "treaty cruisers" (the term "heavy cruiser" was not defined until the London Naval Treaty of 1930