The Diamond was a three-masted square rigger, built in New York in 1823. She was one of the first ships to operate a regular service for passenger and cargo between Britain and the United States. She sank en route to Liverpool from New York on 2 January 1825 in Cardigan Bay. The alleged wreck site was identified in 2000 and was designated under the Protection of Wrecks Act 1973 on 1 April 2002, the first such designation to be made by the National Assembly for Wales. However, the identification has since been called into question.