Ruth Maureen Guy (10 July 1932 – 14 February 2015) was a Welsh mezzo-soprano singer. The youngest of six children of a coal miner, she was influenced by church music in her youth. Guy's debut came at Sadler's Wells Theatre and several of her early engagements were with the London Mozart Players. She became principal mezzo at the Royal Opera House in 1963 and made the first of several appearance at The Proms that same year. In 1969, Guy was selected as one of fifteen soloists to sing at the Investiture of the Prince of Wales and later joined the Opern- und Schauspielhaus Frankfurt in 1972. She took up a teaching position with the Royal Welsh College of Music & Drama which she retired from in 1998 to teach privately at her home in Sageston.