John Hamilton "Jack" Bush (1909–1977) was a Canadian abstract painter. His paintings are associated with the Color Field movement and Post-painterly Abstraction.
In his early practice, Bush was influenced by the work of Charles Comfort and the Group of Seven. During the 1930s, he ran a commercial art business and, by night, furthered his studies at the Ontario College of Art. Bush, like other Canadian artists of the time, was sheltered from major European influences. After seeing the work of the American Abstract Expressionists in New York City, Bush's canvases changed dramatically.
Bush developed his work and approach to abstraction through the 1950s. He was a member of Painters Eleven, the group founded by William Ronald in 1953 to promote abstract painting in Canada, and was soon encouraged in his art by the American art critic Clement Greenberg. Critical at first, Greenberg became a mentor to Bush and encouraged him to refine his palette, technique, and approach. As a result of Greenberg's guidance, Bush became closely tied to Color Field Painting. Bush became friends with artists associated with colour-field like Jules Olitski, Kenneth Noland and also Anthony Caro. As Painters Eleven disbanded in 1960, Bush moved on, and in the end, became one of the more successful artists to come from this group.
Jack Bush represented Canada at the 1967 São Paulo Art Biennial, and in 1976 the Art Gallery of Ontario toured a large retrospective of his work. He died in 1977. Canada Post honoured Jack Bush with a Canadian postage stamp and a souvenir sheet released on March 20, 2009. The stamps featured his 1964 painting, Striped Column and his 1977 painting Chopsticks. His work was the subject of a major retrospective exhibition co-curated by Marc Mayer and Sarah Stanners in 2015.