William George Spencer Cavendish, 6th Duke of Devonshire (21 May 1790 – 18 January 1858), styled Marquess of Hartington until 1811, was an English peer, courtier and Whig politician.

[3] Devonshire had a major interest in gardening and horticulture, and devoted himself sedulously to the care and nurture of his vast estates.

His major projects including the wholesale rebuilding of the village of Edensor, and significant improvement to his several stately houses and their gardens.

He befriended Sir Joseph Paxton, then employed at the Royal Horticultural Society's Chiswick Gardens, located close to Devonshire's London estate Chiswick House, and appointed him his head gardener at Chatsworth House in 1826, despite Paxton being only in his early twenties at the time.

Devonshire, himself a keen horticulturalist, was elected President of the Royal Horticultural Society in 1838, a position in which he served for twenty years until his death.

It was privately printed and provided a history of the Cavendish family's two primary estates: Chatsworth House and Hardwick Hall; the handbook was praised by author Charles Dickens.

Much of Devonshire's private correspondence, including letters to his mistresses (one of whom he installed nearby), was destroyed by his Victorian relatives.