Gwen John was the elder sister of Augustus Edwin John. She studied at the Slade School of Fine Art from 1895 to 1898 under Henry Tonks, a staunch advocate of the importance of a thorough grounding in the art of drawing. In 1898 she travelled to Paris and studied at the Académie Carmen, under James Abbott McNeill Whistler (whose teaching concentrated on painting techniques). She returned to England in 1899 but finally settled in France once again, in 1904. Initially based in Montparnasse, she supported herself by working as an artist's model for English and American women painters, and for Auguste Rodin, who became her lover. In 1914 she moved to the Paris suburb of Meudon, where Rodin had established a studio and 'held court' at the Villa des Brillants. Gwen was also an associate of the poet Rainer Maria Rilke.
In 1913 she followed Rodin's long-time lover Camille Claudel and converted to Catholicism. She remained in Meudon until shortly before her death, eventually building a chalet studio on Rue Babie. The nuns of the town's Dominican convent were among her sitters, together with members of her church congregation. On the eve of war in September 1939, at the age of 63, Gwen travelled to the French channel port of Dieppe, carrying only an official copy of her will and instructions for her burial. She collapsed and died in the town's public hospital on 18 September.
Her works are Intimist in character: small-scale portraits, quiet interiors, her cats or a familiar sitter (The Convalescent) in a frequently-recurring setting. In recent decades, increasing critical and popular appreciation of her work has gone some way towards realising her brother Augustus's prediction that he would ultimately be remembered as 'Gwen John's brother'.
John's works are in the collection of the Yale Center for British Art (Pritzker Gift).