Joachim Gauthier was known for his realistic landscapes influenced by the Group of Seven. He primarily worked in oil and watercolour.

Gauthier was born in North Bay, Ontario. While on a trip to visit his sister in Tacoma, Washington he received an apprenticeship as a sign writer. While there, he began to take life drawing classes under noted sculptor Victor Alonzo Lewis. He was also introduced to painting en plein air and began to document the coastal regions of Washington.
Upon returning to Canada, Gauthier moved to Hamilton with his wife. A few years later, he moved to Toronto and studied under Group artists Franklin Carmichael and J.E.H. MacDonald. Gauthier worked at Sampson Matthews Limited as a commercial artist for 37 years. At the age of 35, A.H. Robson, art director of Grip Ltd., pointed out Gauthier as a young painter with potential, and praised his ability and originality. Gauthier also accompanied Group member A.J. Casson on sketching trips, and he exhibited with the Group. He was commissioned by the McMichael Canadian Art Collection at Kleinburg to do portraits of Tom Thomson, the Group and some of their contemporaries.

Gauthier was elected an Associate of the Royal Canadian Academy in 1947, and became a member of the Canadian Society of Painters in Water Colour in 1931, and the Ontario Society of Artists in 1933. His work is in the collection of the National Gallery of Canada.