Richard Dadd was an English painter of the Victorian era, noted for his depictions of fairies and other supernatural subjects, Orientalist scenes, and enigmatic genre scenes, rendered with obsessively minuscule detail. Most of the works for which he is best known were created while he was a patient in Bethlem and Broadmoor hospitals.

Richard Dadd was born at Chatham, Kent, England, on 1 August 1817, the son of chemist Robert Dadd (1788/9–1843) and Mary Ann (1790–1824), daughter of shipwright Richard Martin. He was educated at King's School, Rochester where his aptitude for drawing was evident at an early age, leading to his admission to the Royal Academy of Arts at the age of 20. He was awarded the medal for life drawing in 1840. With William Powell Frith, Augustus Egg, Henry O'Neil and others, he founded The Clique, of which he was generally considered the leading talent. He was also trained at William Dadson's Academy of Art.

Among his best-known early works are the illustrations he produced for The Book of British Ballads (1842), and a frontispiece he designed for The Kentish Coronal (1840).

In July 1842, Sir Thomas Phillips, the former mayor of Newport, chose Dadd to accompany him as his draughtsman on an expedition through Europe to Greece, Turkey, Southern Syria and finally Egypt. In November of that year they spent a gruelling two weeks in Southern Syria, passing from Jerusalem to Jordan and returning across the Engaddi wilderness. Toward the end of December, while travelling up the Nile by boat, Dadd underwent a dramatic personality change, becoming delusional, increasingly violent, and believing himself to be under the influence of the Egyptian god Osiris. His condition was initially thought to be sunstroke.

On his return in the spring of 1843, he was diagnosed to be of unsound mind and was taken by his family to recuperate in the rural village of Cobham, Kent. In August of that year, having become convinced that his father was the Devil in disguise, Dadd killed him with a knife and fled to France. En route to Paris, Dadd attempted to kill a fellow passenger with a razor but was overpowered and arrested by police. Dadd confessed to killing his father and was returned to England, where he was committed to the criminal department of Bethlem psychiatric hospital (also known as Bedlam). Here and subsequently at the newly created Broadmoor Hospital, Dadd was cared for in an enlightened manner by Doctors William Wood, William Orange and Sir W. Charles Hood.

Dadd probably suffered from paranoid schizophrenia. Two of his siblings had the condition, while a third had "a private attendant" for unknown reasons.

In hospital, Dadd was encouraged to continue painting, and in 1852 he created a remarkable portrait of one of his doctors, Alexander Morison, which now hangs in the Scottish National Portrait Gallery. Dadd painted many of his masterpieces in Bethlem and Broadmoor, including The Fairy Feller's Master-Stroke, which he worked on between 1855 and 1864. Dadd was pictured at work on his Contradiction: Oberon and Titania by the London society photographer Henry Hering. Also dating from the 1850s are the 33 watercolour drawings titled Sketches to Illustrate the Passions, which include Grief or Sorrow, Love, and Jealousy, as well as Agony-Raving Madness and Murder. Like most of his works, these are executed on a small scale and feature protagonists whose eyes are fixed in a peculiar, unfocused stare. Dadd also produced many shipping scenes and landscapes during his hospitalization, such as the ethereal 1861 watercolour Port Stragglin. These are executed with a miniaturist's eye for detail which belie the fact that they are products of imagination and memory.

After 20 years at Bethlem, Dadd was moved to Broadmoor Hospital, a high security facility outside London. There he remained, painting constantly and receiving infrequent visitors until 7 January 1886, when he died "from an extensive disease of the lungs". A number of his works remain on display at Broadmoor.