Samuel Sebastian Wesley (14 August 1810 – 19 April 1876) was an English organist and composer.
Born in London, he was the eldest child in the composer Samuel Wesley's second family, which he formed with Sarah Suter having separated from his wife Charlotte. Samuel Sebastian was the grandson of Charles Wesley. His middle name derived from his father's lifelong admiration for the music of Bach.
After singing in the choir of the Chapel Royal as a boy, Samuel Sebastian embarked on a career as a musician, and was appointed organist at Hereford Cathedral in 1832. While there he married the sister of the Dean, John Merryweather. He moved to Exeter Cathedral three years later, and subsequently held appointments at Leeds Parish Church (from 1842), Winchester Cathedral (from 1849) and Gloucester Cathedral (1865-1876). In 1839 he received both his Bachelor of Music degree and a Doctorate of Music degree from Oxford. He became a Professor of Organ at the Royal Academy of Music in 1850. He died at his home in Gloucester on 19 April 1876 aged 65. He is buried next to his daughter in St. Bartholomew's Cemetery in Exeter by the old City Wall. There are memorial tablets to him in Exeter Cathedral and Winchester Cathedral, and his memorial at Gloucester Cathedral is in stained glass.
Famous in his lifetime as one of his country's leading organists and choirmasters, he composed almost exclusively for the Church of England, which continues to cherish his memory. His better-known anthems include Thou wilt keep him in perfect peace and Wash me throughly. He also wrote several rather late examples of verse anthems, which contrast unison and contrapuntal sections with smaller, more intimate passages for solo voice or voices. Blessed be the God and Father, The Wilderness and Ascribe unto the Lord are of considerable length, as is his Service in E.