Leighton was born in Scarborough to a family in the import and export business. He was educated at University College School, London. He then received his artistic training on the European continent, first from Eduard Von Steinle and then from Giovanni Costa. When in Florence, aged 24, where he studied at the Accademia di Belle Arti, he painted the procession of the Cimabue Madonna through the Borgo Allegri. He lived in Paris from 1855 to 1859, where he met Ingres, Delacroix, Corot and Millet.
In 1860, he moved to London, where he associated with the Pre-Raphaelites. He designed Elizabeth Barrett Browning's tomb for Robert Browning in the English Cemetery, Florence in 1861. In 1864 he became an associate of the Royal Academy and in 1878 he became its President (1878–96).
Leighton was knighted at Windsor in 1878, and was created a Baronet, of Holland Park Road in the Parish of St Mary Abbots, Kensington, in the County of Middlesex, eight years later. He was the first painter to be given a peerage, in the New Year Honours List of 1896. The patent creating him Baron Leighton, of Stretton in the County of Shropshire, was issued on 24 January 1896; Leighton died the next day of angina pectoris.