Canadian provincial flag consisting of a red field (background) with the Union Jack (United Kingdom, flag of the) in the canton and the provincial coat of arms (arms, coat of)—a bison and a Cross of St. George—at the fly end; the flag may be described as a defaced Canadian Red Ensign.

The coat of arms of Manitoba was established by royal warrant on May 10, 1905, based on an order in council of August 2, 1870, creating the provincial seal. The green shield bears a bison, a beast that provided food and clothing to indigenous groups and early settlers and gave the latter a strong export product. The chief (upper part) of the shield was the red Cross of St. George on a white background, the traditional flag of England (England, flag of).

The abandonment of the Canadian Red Ensign in 1965, when the new Maple Leaf Flag (Canada, flag of) was hoisted, led to calls in Manitoba for a distinctive provincial flag. Provincial Secretary Maitland Steinkopf wanted a design competition, while others preferred that the Canadian Red Ensign be adopted by the province. As a compromise it was agreed that the ensign would be used, but only with a substitution of the provincial coat of arms for the Canadian shield. It was felt necessary to have British royal approval since modification of a British flag was involved. This was received in due course, and the first official hoisting of the flag took place on May 12, 1966, the 96th anniversary of the Manitoba Act, which created the province.