May Sinclair, the daughter of William Sinclair, a wealthy shipowner, was born in Rock Ferry, Cheshire in 1863. Sinclair was educated at Cheltenham Ladies College where Dorothea Beale recognised her writing talent.
Sinclair's first novel, Audrey Craven, was published in 1896. This was followed by Mr and Mrs Nevill Tyson (1897), The Divine Fire (1904), The Helpmate (1907) and The Creators (1910), a novel that dealt with the way men denigrate women's creativity. A collection of short-stories, The Flaw in the Crystal appeared in 1912.
Working at the Medico-Psychological Clinic in London in 1913 she discovered the work of Sigmund Freud. This influenced her book, The Three Sisters, (1914) a study of middle-class women in a repressive society. This book marked the beginning of Sinclair's interest in psychology and her attempts to explore unconscious motivation.
On the outbreak of the First World War Sinclair went to France where she worked for the Motor Ambulance Unit. Sinclair was overcome by what she saw and after seventeen days she was sent home to England. Articles based on her experiences appeared in the The English Review during the summer of 1915. A fuller account, Journal of Impressions in Belgium, was published at the winter of 1915.
Other novels by Sinclair include Tree of Heaven (1917) Mary Olivier (1919) and The Life and Death of Harriett Fream (1922). Influenced by the work of Sigmund Freud and Havelock Ellis, Sinclair became one of the leading exponents of the stream of consciousness novel.
Later novels included Arnold Waterlow (1924), The Rector of Wyck (1925) and The Allinghams (1927). She also published two volumes of short-stories, Uncanny Stories (1923) and The Intercessor and Other Stories (1931). May Sinclair, who suffered from Parkinsin's Disease, died in 1946.