John "Jack" Butler Yeats (1871 – 1957) was an Irish artist born in London, England. Son of portraitist John Butler Yeats, and brother of Olympic medallist W. B. Yeats. Though, his childhood was primarily in Sligo with his grandparents, Yeats returned to his parents' home in London in 1887.
His early works are simple lyrical depictions of landscapes and figures, predominantly from the west of Ireland—especially of his boyhood home of Sligo. Yeats's work contains elements of Romanticism. Early in his career he worked as an illustrator for magazines like the Boy's Own Paper and Judy, drew comic strips, including the Sherlock Holmes parody "Chubb-Lock Homes" for Comic Cuts, and wrote articles for Punch under the pseudonym "W. Bird".
From around 1920, he developed into an intensely Expressionist artist, moving from illustration to Symbolism. He was sympathetic to the Irish Republican cause, but not politically active. However, he believed that 'a painter must be part of the land and of the life he paints', and his own artistic development, as a Modernist and Expressionist, helped articulate a modern Dublin of the 20th century, partly by depicting specifically Irish subjects, but also by doing so in the light of universal themes such as the loneliness of the individual, and the universality of the plight of man.
His favourite subjects included the Irish landscape, horses, circus and travelling players. His early paintings and drawings are distinguished by an energetic simplicity of line and colour, his later paintings by an extremely vigorous and experimental treatment of often thickly applied paint. He frequently abandoned the brush altogether, applying paint in a variety of different ways, and was deeply interested in the expressive power of colour. Despite his position as the most important Irish artist of the 20th century (and the first to sell for over £1m), he took no pupils and allowed no one to watch him work, so he remains a unique figure.