William Smethergell was an English composer and musician who lived and worked in London. Christened in the church of St Peter le Poer, after an apprenticeship of seven years, Smethergell became the organist of two London churches, All Hallows-by-the-Tower and St Mary-at-Hill, posts which he held simultaneously for fifty years. He was also the principal viola player at the Vauxhall Pleasure Gardens.