John Thomas (1 March 1826 – 19 March 1913) was a Welsh composer and harpist. The bardic name Pencerdd Gwalia (Chief of the Welsh minstrels) was conferred on him at the 1861 Aberdare Eisteddfod.
He was born in Bridgend, on Saint David's Day, 1 March 1826, son of a tailor, also named John Thomas, a clarinetist in the amateur town band. He was the eldest of seven children, four of whom also played the harp, most notably his brother Thomas Thomas. John Thomas started off by playing the triple harp which had three sets of strings and was very difficult to play. At the age of 14, through the influence of Ada Lovelace (Lord Byron's daughter), he was admitted to the Royal Academy of Music in London. His teachers there included Cipriani Potter for composition.
He taught at the Royal College of Music, where he eventually became professor, and at the Guildhall School of Music.
He wrote many pieces for the harp that are very popular today and are used in the exam syllabus. He also wrote an opera, a symphony, two harp concertos, overtures, chamber music, and two cantatas – Llewellyn (1863) and The Bride of Neath Valley (1866). He played one of his own harp concertos at a Philharmonic concert in 1852.
In 1861, he was briefly engaged to the Belgian soprano Désirée Artôt. He eventually married twice, both times to former students. His first wife, Alice Ann Keate, died in 1880, two years after their marriage; he married Joan Francis Denny in 1885.
In 1872 he was appointed harpist to Queen Victoria.