English botanist and landscape gardener born at Kew, the son of William Aiton. He succeeded his father as superintendent of the Royal Gardens at Kew (1793-1841), additionally assuming control of the neighbouring Richmond Gardens when John Haverfield retired 1795, the royal gardens at Kensington Palace, Buckingham Palace and at the Royal Pavilion, Brighton.

Aiton was one of the founders of the Horticultural Society of London (1804), later to become the Royal Horticultural Society. Aiton continued his father's work with the second edition of Hortus Kewensis, the type material of which was also sent to Banks, and acquired by BM. With the deaths of Joseph Banks and King George III in 1820, both royal funding and interest in the gardens waned. Aiton was restricted to responsibility for the gardens at Kew as they fell into decline. The gardens were eventually transferred to the nation in 1841 and Aiton handed over control to W.J. Hooker as the first Director, before retiring in 1845. The herbarium at K was not founded until 1841 and specimens created at the gardens before that time were sent to Joseph Banks, held privately or deposited at BM. Aiton's private herbarium and library were sold by Foster and Son in London on 4 September 1851.