Robert Lucas Pearsall (14 March 1795 – 5 August 1856) was an English composer.
Pearsall was born at Clifton in Bristol on 14 March 1795 into a wealthy Quaker family. His father, Richard Pearsall (died 1813), was an army officer and amateur musician. He was privately educated.
In 1816 Pearsall's mother, Elizabeth (née Lucas), bought the Pearsall family's home at Willsbridge, Gloucestershire from her brother-in-law, Thomas Pearsall. Thomas had been ruined by the failure of the iron mill that had been the family's business since 1712. However, after the death of his mother in 1837, Pearsall sold Willsbridge House. Despite the fact that he would never live there again, he regularly chose to be known in publications as 'Pearsall of Willsbridge'. As for Willsbridge Mill, it was later converted into a flour mill, and it stands to this day.
Pearsall married Harriet Eliza Hobday in 1817. She was the daughter of a moderately successful portrait painter, William Armfield Hobday (1771–1831). The couple had four children—two boys (although the first son died in infancy) and two girls—all of them born in Bristol. In their early years of marriage, Pearsall practised as a barrister in Bristol, but in 1825, he took his family to live abroad: first to Mainz, then to Karlsruhe (1830–42). In 1842, evidently after a long period of strain in their relationship, husband and wife separated. Pearsall used the money from the sale of the house at Willsbridge to buy the Wartensee Castle, a ruined medieval keep near Rorschach in Switzerland; immediately following his purchase of the castle, he spent several years restoring the keep and building a suite of apartments adjacent to it. He remained there until his death on 5 August 1856, and was buried in the vault of the castle's chapel. When the chapel was deconsecrated in 1957, his remains were removed and reinterred at the Roman Catholic church at Wilen-Wartegg.
Pearsall's move abroad brought opportunities to develop his interests as a composer. Although it seems likely he had some instruction, or at least received advice, in composition from the Austrian violinist and composer Joseph Panny, most of his early attempts would appear to have been self-taught. There is little evidence to support a claim made by Hubert Hunt that his early works included the Duetto buffo di due gatti, published under the pseudonym G Berthold and often attributed to Rossini. Though resident abroad, he kept in touch with his home city of Bristol. Pearsall's last visit to Willsbridge in 1836–37 coincided with the foundation and earliest meetings of the Bristol Madrigal Society, for which many of the madrigals and part songs he wrote in the period 1836–41 were composed. The success of his earliest works for the society encouraged him to write others, including 'The Hardy Norseman' and 'Sir Patrick Spens' (in ten parts), and eight-part settings of 'Great God of Love' and 'Lay a Garland'. His setting of 'In dulci jubilo' (in his original version for eight solo and five chorus parts) is still performed frequently at Christmas.