Mr and Mrs William Hallett is a 1785 oil on canvas painting by the British painter Thomas Gainsborough, and is now in the collection of the National Gallery in London.

Thomas Gainsborough was an English portrait and landscape painter, draughtsman, and printmaker. Along with his rival Sir Joshua Reynolds, he is considered one of the most important British artists of the second half of the 18th century. He painted quickly, and the works of his maturity are characterised by a light palette and easy strokes. Despite being a prolific portrait painter, Gainsborough gained greater satisfaction from his landscapes. He is credited as the originator of the 18th-century British landscape school. Gainsborough was a founding member of the Royal Academy.