Catherine Sinclair (17 April 1800 – 6 August 1864) was a Scottish novelist and a writer of children's literature which departed from the moralising approach common in that period. She is credited with discovering that the author of the anonymous Waverley Novels was Sir Walter Scott.
Catherine Sinclair was born in Edinburgh on 17 April 1800, the fourth daughter of Sir John Sinclair, 1st Baronet and Lady Diana Macdonald. Catherine died unmarried. Sir George Sinclair, 2nd Baronet, John Sinclair (1797–1875), and William Sinclair (1804–1878) were her brothers. She was her father's secretary from the age of 14 until his death in 1835. From 1814 to 1818 she lived at Ormeley Lodge, Ham. She was an aunt of the novelist Lucy Bethia Walford.
Sinclair then began to write independently, her first works being children's books, prompted by an interest in her nephew, the Hon. George Boyle, 6th Earl of Glasgow. Her story of two anarchic children, in Holiday House, A Book for the Young, successfully engaged the imagination of her young readers. This work was a popular and notable example of the genre, for it departed from the moralising approach of other works for children in that period. It also encapsulates a fantasy tale of fairies and giants.
On the subject of children's literature, Sinclair remarks in her preface,
"But above all we never forget those who good humouredly complied with the constantly recurring petition of all young people in every generation, and in every house, — 'Will you tell us a story?'"
Sinclair's activities in Edinburgh included charitable works such as the establishment of cooking depots in old and new Edinburgh, and the maintenance of a mission station at the Water of Leith. She was instrumental in securing seats for crowded thoroughfares, and she set the example in Edinburgh of instituting drinking fountains, one of which bore her name and stood at the city's West End before it was removed as an obstruction to trams in 1926. Sinclair is also noted as being the discoverer of Sir Walter Scott's authorship of "The Waverley Novels" which were originally written anonymously.