Nelly O’Brien (d.1768), well-known beauty and courtesan, was a friend of Reynolds who used her as a model for his ‘fancy pictures’ and painted her portrait on several occasions. The present picture was painted during the period when Miss O’Brien was enjoying the protection of the 3rd Viscount Bolingbroke, to whom she bore a son in 1764. The artist demonstrates great ability in depicting the different textures and delicate colour harmonies of the sitter’s costume, as well as the luminous effects of shadow and reflected light on the sitter’s face and bosom. The painting was much admired by contemporaries and frequently engraved.