Canadian painter who was a member of the Group of Seven (Seven, Group of), a group of painters that forged a national identity through the visual arts with their paintings of the Canadian landscape.

From about 1913 Casson studied at schools in Hamilton and Toronto, before joining a commercial art firm in 1919. There, he eventually worked under Group of Seven member Franklin Carmichael. The two became friends, and in 1925 they attempted to revive interest in watercolour painting by organizing (along with Frederick Brigden) the Canadian Society of Painters in Watercolour. The next year, Casson was invited to join the Group of Seven, replacing Frank Johnston. By then the painters had turned from exclusively depicting harsh landscapes to also including urban scenes. Casson distinguished himself from the rest of the group by painting small Ontario villages, as in Anglican Church at Magnetawan (1933).