The eldest of seven children in a Ukrainian immigrant family. His parents were farmers and did not encourage any early interest in art that William had. He studied at the Collage of Art in Toronto and in Mexico at the Instituto Allende, but he was primarily self taught.
In 1952 while living in England Kurelek experienced an emotional breakdown. Suffering from clinical depression he was hospitalized. He was treated for schizophrenia. While in hospital he painted, this work was later used as a cover of the Van Halen rock album called THE MAZE. He was transferred to another hospital where art was used as therapy, He produced three masterpieces, "Where Am I", "Who Am I", and "Why Am I".
In 1959 back in Canada, William applied for a job making frames, he took along three or four to show how serious he was in wanting the job; this resulted into an exhibition for him. His first exhibition in 1960 was an immediate success.Inside of 20 years He produced more than Kurelek is popularly known as a painter of Western Prairie scenes, in fact the scope of his work is enormous, covering political, social, ethical, religious and historic themes.
Toward the end of his life, his heritage became pronounced; he was nearing the end of his life and was ill when he visited his father's village village in the Ukraine to research material for his work. He returned 3 weeks later with 100 drawings and 6 paintings, soon after this he entered hospital touching up drawings until he died.